Where can I get government funds to help modify my mother's bathroom?

Medicare does not pay for an aide. This only happens after a hospital stay and an order for in home PT where an aide is provided. Its temporary. A lot of services provided are based on income. Unless things have changed in the last ten years, Medicare does not provide shower chairs.

It might be as simple as changing to a hand held shower and a pivoting bath chair where she sits outside of the shower and swivels in. If you visit any assisted living, there are no tubs. In one IL that my mom lived, her fiberglass tub had a retrofitted opening in the side wall to just walk in.

Contact elder services - have someone help you find a CNA ( certified Nurses assistant ) who can help with Bathing . Medicare will pay for that and provide the needed equipment .

Call your Office of Aging and see if they can evaluate your house. There maybe programs available. Like Willie suggested, a shower bench. Transfers are nice but my bathrooms aren't configured for them. Handheld shower head is great. They have longer tubing if needed. There is a bar that attaches to the tub to gave something to hang on to. You can get suction cup bars temporarily. I recommend a commode over the toilet. IMO, they are more stable than a highriser with sides.

Maybe there is Habitat for Humanity in her area? They have an Aging in Place program:

https://www.habitat.org/our-work/aging-in-place

my mom just got a shower chair as she was unsteady standing in the tub even with grab bars. Sounds like that’s not enough for you’re now. Good luck!

Contact Medicaid in your area and see about any programs to make bathroom more accessible.
I think these programs are overall rare and normally the federal government doesn't pay to make our homes more accessible for us. I have heard that in some states with very generous Medicaid programs there is some funding for ramps and other items; I would seriously doubt that a bathroom would qualify for anything other than pull bars and etc.
But you are free to check with Medicaid workers for number to call, or call for your State and ask.
Good luck.

In the mean time a transfer bench, a hand held shower wand and sturdy grab bars are fairly inexpensive adaptations that can make washing safer for her. Consider getting something for the toilet as well, either a seat riser and grab bars or a freestanding commode that can be placed over the toilet.

You can try calling 211 to see what resources may be available for your mom, along with calling your local Area Agency of Aging, and Senior Services.
And of course if being on her own is just too difficult for your mom, it may be best to have her placed in the appropriate facility where she will be looked after 24/7, and her Medicaid will pay for.