Paintball CO2 tank refill recommendations?

Hi, folks,

I am looking into paintball CO2 tanks as an alternative to Sodastream canisters for carbonating water. Problem is finding a place that will refill them inexpensively, preferably near the inner loop area. Conventional Googling says that the sporting goods stores should refill them, but the big ones I've checked (Academy and Dick's) won't offer the service. Anyone else try? Or is there a better option? It isn't kegerator level stuff, just trying to have a regular supply of carbonated water without breaking the bank or wasting much plastic. Thanks for the help