Clown loaches would be awesome but do need large tanks.
Yo Yo's might be a better option, max size is about 15cm. Zebra Loaches only get to about 10 cm. Dwarf chain even smaller - about 6cm.
I've only ever had Zebra Loaches, and only managed to get 2 of them. Despite recommendations they are happier in groups of 5+ as they are a shoaling fish, seemed to do fine as a twosome. One died a few months back and the one left still seems happy enough, he's started hanging out with the tiger barbs.
I don't know how readily available they are as I've only seen them twice at my LFS and one of those times was when I bought them. They were around the $12 mark from memory.