La Pulga de Alamo. No seriously, some of those places can work wonders on cell phones. Any of the big flea markets have places that fix while you wait or shop
Edit for further info. A lot of the flea markets have weekdays now, they are no longer only weekend deals. I wish I knew more specifics, but there is a big one in Palmview that goes during the week and same with the one on Valverde road in Donna.
Wife is saying that there is a good place in McAllen off of 10th, on the left as you head north, next to Espi & T's Mexican food. Just north of 495 and across from the pawnshop in a strip mall.