My mother has a semi electric hospital bed. It took six months for the paper work to go through but it was worth it. She has severe spinal stenosis so Medicare paid for it. She also got a gel mattress at the same time. What a difference turning and changing her. The hospital bed was new and Medicare rents it until 18 months of use then the patient can keep it. I would ask the doctor write a script for both bed and mattress pad.
Contact one of your mother's doctors. His/her staff can determine if your mother's current illness qualifies for a hospital bed, and order one through a DME, which will deliver the bed to the home.
There may also be beds available for loan through local Senior Centers.
If your Mom in on Medicare, see if her doctor will write an order for a bed. Be aware though that Medicare rents the bed so it may have to be returned to the provider when done using it.
Contact Council on Aging in your area. They can tell you what resources are available. Have he doctor write a script for one. Is your mom on hospice? You can get a hospital bed from hospice.
There may also be beds available for loan through local Senior Centers.