L400s and L450s are the first 2 that come to mind after the zebra pleco, which would cost you quite a bit more to get. They are not readily available, but there are a few around. Both are banned from export from Brazil. Both stay under 6" long, which makes them ideal for smaller tanks (No, I'm not calling a 55 gal small. My biggest pleco breeding tank is a 40 breeder.) And if you buy sub adults, they grow faster than zebras AND, they will cost you less $. Good luck.