The rubber-lipped plecs usually stay under 5 inches and are relativly easy to find and inexpensive.
I'll second that. I have three bristlenoses in two tanks, a Clown Pleco, and a rubber-lip (bulldog) pleco. The bristlenoses are great algae eaters once they get over about 3". The Clown Pleco is seldom seen and apparently Never eats algae (pretty fish if you can spot him, though). The bulldog, though... at under 2" keeps a 20 gallon high spotless enough to starve the ottos that were in there.
The one thing about bulldogs, though: they're not precisely tropical. You can keep them in a typical tropical tank, but, very like white clods, they prefer a lower temperature, goos water movement, and a stream bed type bottom. Oh, and they like to hide under things.
Back on bristlenoses for a second:
Ancistrus cirrhosus is one of a half dozen species. Some of them get as long as 8", but 5" is a more usual max size. If you're going to spring for the shipping from aqua-bid, buy yourself an albino. They tend to stay under 4", and they are gorgeous in an admittedly Lovecraftian sort of a way.
The other neat thing about Bristlenoses is, from everything I have read, they are the easiest of plecos to breed.