Depends on where you gonna be. Where i the wedding?
Piranha Records is a good store, they stock all the local texas shit from austin to houston and got the new shit in. It's in ROund Rock, a little north of Austin, but worth the trip. They got all the screw tapes on CD, etc.
In austin, you got Music Mania, but they overpriced and only fuck with the big times usually now. I don't know if Backstage music is still open, but if they are look em up, they a house in the east side and got all the underground shit and all the mexican shit, run by some mexicans so you will have some luck there. There's a big flea market outside of town on highway 290 I think, but I forgot the name of it. Also you can try to look up the DOllars n Sense store, Top Dollar Clothing, don't know if they still have a store. Also try to hit up DJ Rapid Ric or J. Kapone - both mexicans both big down in Austin, they can probably help you out.