I work for an agency that pays respite providers for care like you're needing. Many of the families we serve have a family member or close friend become their respite provider. I don't know all the hoops that they need to go through, but they can be paid for the respite care and you can work with someone who is more likely to be responsive to your needs and with whom flexibility and reliability can be achieved. You can also feel good knowing that the person you're leaving them with is personally invested in your mother and her care.

I don't know if you have anyone that could fit this bill, but it might be worth a try if you can think of someone.