Well for a 55 I would stick to a plec that stays under 10" full size. As to not eating plants, well, that is kind of hard to do, if you feed them properly they will not harm your plants much at all. A healthy planted tank can sustain several plecos, without damaging the plant life, as the plants will grow back faster than they can be eaten. Now a fancy plec that does not need driftwood indicates for the most part a carnivore. One that will eat algae will also need wood, it is kind of a package deal.
Now we need more specifics, what are your parameters of the tank? What kind are you looking for? Striped, colored, spotted, common colorations, BN, rare? How much are you willing to spend? Do you have some form of sanctuary where this plec could hide, since you lack wood? With this knowledge we can help point you in the right direction.