Time for a chair type of commode. Can anyone recommend an alternative that I can put in her bedroom please?

Before buying something you should see if your area has a free medical equipment bank. In my area there is one run by volunteers who give out all sorts of equipment that has been donated. When I was there I saw a volunteer almost turn away a commode because they already had so many. They also had shower chairs and benches, crutches, walkers, wheelchairs, and more equipment, plus mounds of packages of Depends type products. All given away for free. The space to store all of this is donated by a local funeral home, and has limited hours of operation. Nice idea if someone is looking for a volunteer project.

Commode. Medicare will pay for it with a doctors order. My mother has one paid by Medicare.

https://www.medicare.gov/coverage/commode-chairs

Good news, Medicare will cover a commode if scripted by the doctor and purchased through a registered DME provider.

I don't recall if commodes were covered by Medicare, but my best recollection is that they were not.

Follow Barb's suggestion, check out the various options, then visit your local DME suppliers to see what's offered.    In my area, DMEs are both stand alone and affiliated with hospitals.  

Something you might consider, and I'm not sure if it's been addressed since we purchased them, is the tipping possibility.   Perhaps they're more stable now, and this isn't an issue.   But you might also investigate stabilizers for the legs.    A DME store could help you with this, but you can also search online.  As I recall, there were a number of options.

If you type "bedside commode" into Google, you will find lots of different models.

There are bariatric models for large folks, ones with covers, all kinds of modifications.