It may be easier to remove the pedestal sink and install a mini vanity with a mini cabinet for storage. My half bath is a scotch larger and NOTHING is stored except what fits in the medicine cabinet. It is next to the kitchen that has lots of storage.

I'd try to find something like this with measurements that would fit to the right of your toilet (where your TP is currently sitting).

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I once had a small open table like this next to the toilet in a bathroom with zero storage. I got a cool basket for the bottom for toilet paper. The draw fit feminine products, a nail kit, some extra medine, neatly organized with a drawer divider.

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You could also hang a small shelf to the right of the sink to place objects on like a box of kleenex, q-tips, sunscreen. (Not sure what you want or need to store in here.)

I’ve seen cabinets or shelves built over the door in small bathrooms like that which require a stool or step ladder to access.

For some reason all these look a little weird

What do you need to store beyond an extra roll or two of TP?

And, just curious, what’s out the window? Is that an air shaft? Outside? ”Used to be outside now it’s enclosed utility space”? Can you remove the window and turn the cavity into a cabinet? Apartment, condo, or coop?

I have a smallish powder room that also serves as a guest bath since it has a small shower. I added two ledges by the sink, and a small chrome three-shelf unit from Bed Bath and Beyond (RIP) for extra tp and towels. It fits between the pedestal sink and the wall to its left.

Friends of mine added a little powder room to their 1910 four-square. They put a shelf above the bathroom door, to store extra rolls of TP.

Looks like you need to use the wall for space and keep it at the leaast amount of stuff.