Bristlenose, meyersi, hillstream loaches, butterfly pulcher--there a many 'pleco' type fish that will stay under 4-5 inches. Otocinclus are even smaller, staying under 2 inches for most species.
The better question is: what do you want the fish for/ If it's to be a worker fish, than some types are better than others. Many are good algae eaters as juveniles, but not as adults. All must be fed appropriately, probably different foods than many other community fish prefer. You don't have to have a pleco in every tank, and if you're not interested in a specific fish, it may be better to avoid them.