How can I assist my wife toileting if I can no longer lift her?

Ask an occupational therapist to come to your home and assess your routines. They are the experts in solving problems like this and will be able to advise you on the right equipment (if needed) and how to use it.

One further point to think about: the OT will advise your wife as well as you. Don't forget that she is an autonomous adult with at least equal responsibility for managing her own needs. It's too easy for an able-bodied caregiver to start thinking s/he has to do all the work.

Wouldn't a bedside commode be easier?

There is an awesome piece of equipment that you could use called a Sit to Stand. As long as she can hold on to handles this would help a lot. Once you have a safety belt around her you hook the belt to the lift and it will help you lift her to a standing position. You can then place her on the toilet if you can get the equipment into the bathroom or you can place her on a commode. Or if she is wearing briefs you can easily change her while she is standing begin supported by the equipment.
This would be safer than trying to use a Gait Belt to assist her in standing.
Another option would be to hire someone that can help you on a daily basis. This might be safer for you as well as your wife. Safety should be a priority both your safety as well as your wife's. You don't want to risk injuring yourself while helping her and you don't want to risk injuring your wife.

Your profile says you are old and tired. Being tired is a way of life for caregivers. Being old, as you say, adds additional risk. Assisting her to the toilet is not a once a day thing; it is several times a day and if you can lift her, and it sounds like maybe she cannot stand on her own, maybe it is time to re-evaluate your living situation. I bought a combination toilet riser seat with build in rails that made it easier for my inlaws to get up from the toilet. But if your wife cannot stand, that complicates it. Not being able to get on and off the toilet is one of the basics of living independently. When someone cannot do that anymore, that is an indication that there are lot of other things they cannot do. And having to do it for them, puts the caregiver at risk. For better or worse, does not mean you have to injure yourself to provide care. You can still be a good husband if you ask for help. Using a lift to put someone on a toilet is a 2 person job and not that easy. Doing it several times a day risks injury for everyone. Considering a move to assisted living, if you both go, has a lot of effort attached to it and that might be hard to get your head around. If you have family, either near or far, it might be time to discuss some options with them; this toileting question is likely the tip of the iceberg.

Oh my goodness, no no, of course you would need training for the lifts but if you are caring for someone at home who cannot move you need something to assist you or you are going to hurt yourself and them. Did you know that anytime you lift more than 35 pounds you put your back at risk? I had never heard of that but my goodness how many of us caregivers are doing that everyday?!

Medicare does pay for an Occupational Therapist visit, maybe accessing an OT to come and evaluate would help as well.

Is she totally bedridden or in a wheelchair full time? If so, Depends are your only option. If you can’t change her and clean her properly, she will probably need to be placed with professional care, either at home or in a facility. Trying to lift her or use an assistive device can be dangerous for both of you. My heart goes out to you. For awhile, I had the same problem with my husband and it took 3 of us to help transfer him to the toilet, and we used a bedside commode. He had surgery and got strong enough to transfer himself for now, but we all know if he can’t do this for himself in the future, he will need professional care. We are doing what we can now to financially prepare for what may come. (((Hugs)))

Do you have access to HomeHealth? Talk to her doctor & request services for her. If he says No. Call a Home Health care (ask friends for a good one) . They can help out A lot . Even if you are home also. that doesn’t matter. Yes you need assistance OK you don’t want people to “think that you can’t take care of your wife”. “Finally he got outside help “
Remember the good days🙂

I hope you already have a riser on the toilet and good sturdy grab bars? And I was surprised at how helpful some very easy PT exercises were in increasing my mom's abilities, at least for a while.
I think that the bottom line is that this is the point where many caregivers realize they can't do it any more and make the painful choice to transition to a facility. It's OK if that is where you are at, it takes a village and at a NH there are many hands to help both of you.

I don't know if you have ever seen the lifts that are available for home use. There are power versions as well as assistive versions if your loved one can still participate in moving.

They range in price from a few hundred dollars to thousands of dollars but they definitely make moving and transitioning much easier. Medicare may or may not cover some or most of the cost if you can get her doctor to write a script for it as part of her care.

I did a quick Google search and came up with this https://www.medicaleshop.com/patient-lifts - there are hundreds of sites that have varying products.