While it might seem difficult and dangerous, you likely know your own shower well enough that you would be able to find the soap with the lights off. Try turning them off right before getting undressed.
The first few times you try this, you could have a (preferably waterproof) flashlight nearby. If you need it, you can use it for a few seconds to find things.
Put the things that you need in a different corner of the shower before you turn the lights off for ease of finding it