You seem to have a problem. Just use a damp sponge. Anything more will
be too heavy for the structure of the house.

More helpfully, I did come across a fibreglass shower cubicle once in
the plumbers merchant. It consisted of 3 or 4 cross sections through
the shower cubicle that stacked on top of one another with widely
overlapping joints. It was claimed to be leakproof-ish, and I can
believe that. I can't remember how the door was done. Perhaps a curtain
would be better? I've never seen another one like it, but it sounds just
like what you might want.

Try googling sectional fibreglass shower cubicle. That brought up, for
example:
https://blog.advanced-showers.com/en...ss-shower-pods

If you look at their brochure you'll see that they have fibreglass
shower pods that stack in the way I described.