How can I install non-electric lighting in a shower stall?

Try installing solar power outdoor lights on the shower where they can get at least 6 hours of sunlight a day......you may have to move them around for best results

I have a shower curtain that has a translucent upper panel. I love it. It made all the difference before we had light in the shower. You can also use little Puck lights that are LED and run on a single battery. These turn on when you push the top of the light, so you will need to put them within arm's reach.

Here's some battery powered choices...Good luck!

https://www.amazon.com/Mr-Beams-Wireless-Battery-Operated-Motion-Sensing/dp/B002FCNLHK

Puck lights should help to solve your problem. Just be sure to place them above the water source. The LED ones provide a great deal of light and batteries last a long time in them.