If it's like here in the NW corner of the state, cheapest is usually welding supply shops. They have the equipment to actually pressure fill a tank. Keep calling, those welding shops you contacted must get their tanks filled somewhere. Most Distributers can only equalize from a larger tank. Which means that if your the first fill from a large tank your in good shape, if your the last, well you get whatever remains in the tank.
Also call a few local bars. The get their tanks filled somewhere too.