I know of a good place (I am in VA)
there's a place called "Fox Mill Pets," they have two stores, both are in Herndon. You want to go to this address for your crowntail /halfmoon or whatever you want:
13300 Franklin Farm Road · Herndon, VA 20171 703.464.0962
I was there this past weekend and I bought a royal blue butterfly halfmoon male (that's a mouthful) for about $9+ tax. It's a bit more than what you're willing to spend, but its a better selection (in terms of their health and how they keep them) compared to PetCo in herndon (which also sells crowntails for the same price but in much worse condition).
Just give them a call, they said they usually get new stock on wednesdays (but be sure to call) and the fish guy that helped me out said he wasn't sure of their age but he's had his live way past a year and they are kicking (so they are relatively young).
Tell me how it goes.
Oh and if you are in Richmond /Ashland then you might want to try a place called Fin and Feather. They treat their animals well.