My husband had a stroke a few years ago and now must use what we call a shower chair. We have used https://www.amazon.com/dp/B000VYK87U for about 2.5 years and have had to replace the foot pads once...of course this is with daily use.
When we travel and stay anywhere we have to be cognizant of bath time. If we are going somewhere by car, we take his chair even if we've been assured our destination has one (we will not stay at a certain hotel chain any longer - enough said). A shower chair is impossible to carry/transport on a flight.
It is extremely frustrating not to mention humiliating to him to have to explain to hotel clerks what a shower chair is and hope/pray they find the one we were assured when booking.
Note that shower chairs accommodate people of different weights. I'd ask this person what their weight is and buy a chair to accommodate them or at least 300lbs. Also make sure you have a rug or none slippery surface for them to exit the shower.
I think Ellen's response is spot on. Help your guest have a nice break from the normal drudgery of life and do so in a way that preserves their dignity.