Since you said you have wall space, why not do recessed shelves or a small recessed medicine cabinet? It take up less space and gives a cleaner look IMO.

CHeck the bath fixture dept at Lowe's or Home Depot.

Recessed is a lot of work, so I can totally see why you'd want a small set of shelves.

It's hard to recommend a place to buy things, because each town can be so different.

Am I right in guessing that you want shallow shelves?

Ikea has interesting wall shelves.

The Command adhesive people (3M) make stick-on wall ledges that will hold the most-used stuff.

the Wayfair mail-order place (they have a website) has pretty decent stuff.

One term to consider searching on is "wall shelves" or "display shelves"

https://www.wayfair.com/storage-organization/sb0/wall-display-shelves-c45770.html

You could also look into "bathroom wall cabinet" (I found a shallow cabinet from BB&B once, but of course it was a one-time-only thing)

Or look into medicine cabinets w/o mirrors.

And look at "bathroom wall shelves"--there are options there.

depending on the stores you have, I'd wander through:

Pottery Barn

Home Goods

At Home

And look not just in the bathroom area but also in the "displaying knicknacks" area.

also look here

https://www.wayfair.com/storage-organization/sb0/bathroom-cabinets-shelving-c1826530.html

what is your comfort level with "easy to install"? Can you drill a hole in the wall for a wall anchor?

Or are you willing to hire a handyman to do something like that? (Shouldn't be expensive--and it isn't particularly difficult for most relatively handy people)

And how much do you think you'd want to put on there? Toiletries can be heavy, since they've got all that water in them.

That might help shape some of the suggestions.

When it comes to "small" and "easy to install", I think of Ikea. You didn't say how much space you have, in a horizontal or vertical dimension, but there are lots of options: shelves that are also towel racks, narrow shelving unit that includes a towel rod, or even a combination of shelves, bins, and hooks.