Fully grown bristlenoses couldt be an option, and like i said before a Hypostomus at 6 inch would be a great addition,.
They are pretty common available and wll noy outgrow yout tank.
Or a fancy Pseudacanthicus. they come with beautifull red tails, but look a so spiny.
Or get yourself an oddball pleco, allthough this may be a bit hard , due to the pleco export ban.
Any pleco between 6-10"wouldt do fine.
Go get an Oligancistrus, maxes out at 7 inch.
No, that's mean, for i know nobody on any forum or in real lif ewho has this fish as well.
It's not even described in the Aqualog yet.
Uberrare... but you'll find something nice.
Just take your time.
I found a hobby importer who taught me a lot and most of my plecos came from that Plecofanatic guy and are doing fine, after the first years.