Does anyone have advice? My mother is 91, has dementia, against leaving her home but having issues with incontinence.

How long has your mother been living with you? What are her assets?

Are you an only child? (Why did she come to live with you?)

There may be an UTI that needs ruling out?

But assisted toileting now sounds necessary.

As dementia is progressive, the needs change & are progressive to.

There comes a time for supervision with daily tasks.

I am not a fan of cameras for this. A camera does not stop someone trying to cook the electric kettle on the stove or overfill the toilet. Close supervision & hands-on help: to assist, direct, re-direct & calm becomes necessary.

It sounds like you have reached that point.

A current needs assessment may be a good starting place.
Then research what is possible, financially & available in your area.

It will come down the least worst outcome of;
A. Keep aging in place: with all day supervision by an Aide at home.
B Move into care: where supervision already exists. Eg staffed memory care.

Mother will not want strangers. But it becomes about what she NEEDS. You cannot be home all day & also at work.

A bigger care team is now required.

According to your profile you live with your mother and still work outside the home several days a week, leaving her home alone.
You also say that her memory issues have gotten much worse, along with her incontinence issues.
Those 2 issues alone, mean that she is no longer safe to stay by herself while you go to work. You're either going to have to quit your job to care for her 24/7. or you will have to hire some part-time or full-time help(using moms money)to come in to assist her. She should NEVER at this stage she's in be left alone.
And of course it realistically is probably time to be looking into placing her in either a memory care facility of skilled nursing facility, as then you will have someone to care for her 24/7 and you will know that she is safe and you can get back to just being her daughter.
There's no easy answer here, but you must now do not only what is best for your mother, but for yourself as well.
I wish you the very best in making some hard decisions.

Can you get caregiver for those hours?

Who does Mom live with?
Who has POA?
Has placement been considered?