I use wire shelving units. They come in different lengths and heights and you can hang lighting fixtures on them.

Here is a link that might be useful: This might work

Are you looking for something specifically to fit over a toilet?

I use the Gorm series wooden shelving system (see link below) for my plants, but not over a toilet. They are nice and sturdy; each shelf has a 77-lb weight capacity. The width is 30 3/4" and they come in different shelf depths. That might be a little wide for your space but don't know.

I actually took the one with deeper shelves, cut it off at waist height and made the bottom part into a potting bench and then took the leftover top 2 shelves and made them into little benches for my plants out on my patio. They hold up to the weight of the pots very well. My daughter stained it with a redwood deck stain/sealer and it looks great. If you are looking for something specifically over a toilet, you could possibly do the opposite, leave off the bottom shelf and move the other 2 or 3 up over the toilet. You'd still want to use the brace in the back to support the legs, since it wouldn't have the support from the shelves and if used in a bathroom, definitely would want to seal it to protect the wood.

Hope that helps

Laura

Here is a link that might be useful: Wooden shelving from Ikea