You can request both shower benches and toilet seat risers from Housekeeping. You don't need to be in an accessible room. They can't be reserved ahead of time, so there is no guarantee that they will be available.
We have gotten bath benches - they were the very basic, inexpensive bath benches you can get at any home improvement store. If you get any equipment, be sure to check for loose screws/bolts. The bath benches that were brought to us had dangerously loose bolts.
For those reasons (and if you need something less basic), I would recommend renting from an offsite medical supply company. CARE is a good one - you can get their contact information from post 2 of the disABILITIES FAQs thread near the top of this board or from the link in my signature.