First of all your common pleco is going to get big, and messy. It would be my reccomendation to trade it in before it gets large.
Uaru have a large distribution, in the Amazon-SolimÃµes River drainage from the JapurÃ¡ River to the TapajÃ³s River, and in the middle and lower ***** River basin.
There are a lot of different species of catfish found over this vast range. So it really depends on what your looking for from your catfish.
For cleaning up scraps of food, you can't go past corydoras.
For trying to keep algea under controll, bristlenose plecos have a decent reputation. However you can't expect them to subsist purely on algea growth in the tank, especially as they reach maturity, and do have to feed them algea wafers and vegies like sweet potato, zuccini and cucumber. Many keepers of bn's have noted that once they attain full size they slack off on the algea eating duties.
Otherwise, there are heaps of smaller fancy plecos found over this area, and your only limited by your budget and what needs different plecos have, mostly dietry. Here's a link to a small list, http://www.planetcatfish.com/catelog/se ... order=hits
just hold your curser of each name, and a picture of the catfish will pop up.
Personally I'd go for a single starlight bristlenose, Ancistrus dolichopterus, and a trio of one of the samller panaque species, only becuase they are are vegetarians like Uaru, and would eat any uneaten vegies you feed to your Uaru.
Oh I nearly forgot, you don't have to buy at Walmart or where ever. For catfish check out here, http://www.plecofanatics.com/forum/foru ... y.php?f=58
Also check online to find out if you have a local aquarium society or cichlid club. If you do, many have a website with a forum on, and fair bit of trading will go on here. Also while C-F may the busiest cichlid forum, many states and cities will have a local aquarium or cichlid forum, and you will hardly ever have to buy at an LFS again. And prices are easily one third of the of those in LFS.