There are lots of online stores with cheap delivery such as CHEAPFISH and LiveAquatics. I am not sure on quality of stock though.
They need a BIG tank too, minimum is said to be 75 gallon but I wouldn't recommend keeping them in anything smaller than a 125 gallon. Subdued lighting is preferred as they are skittish fish and if this is a problem you may get away with a load of floating plants. pH below 7 and as obvious a species only tank, you could try with a pleco but personally I wouldn't try it. Bear in mind that they will reach a foot long but this will take several years so they can be grown out in a smaller tank. Good luck