I tried Metroplex Welding in Fort Worth, but he said he would have to order 30 tanks. Can't find a Fort Worth Welding supply. Do you have a number? So unless we want to start a group buy.....
Try fire suppression guys. The guys that fill fire extinguishers. Also the homebrew beer store guys know where to get filled. FYI Generally the welding CO2 is no purer than any other vender. I personally use Koetter near royal and 35 in dallas. They checked the bottle and filled while I waited. Hope that helps some.