What is wrong with the shower handle? Loose? Too tight? Leaking? Not working?

The smallest I've seen was 30 x 30, a bit tight for me. Standard is 36 x 36 inch,

There are some glues in caulking tubes that would probably work. Not Liquid Nails. You would have to place and glue the bottom, then the sides and cut lengths of wood, 1x2 to wedge between the two uprights. Tight enough to hold them tight against the wall or shower enclosure. Letting the glue set at least overnight.

A recessed light fixture with a rubber gasket approved for use in a damp location, e.g. shower light.

Blow dry your hair down when you're out of the shower. Then put on a beanie tight beanie then go to sleep.