Desperado-
As a "bambulance" driver at one time myself... he should have restocked you. Call the company and complain to the shift manager. I've been refilled a few different times when I helped out first. Also, it's probably appropriate to complain about the patient care - Cspine, tourniquet removal, etc. You might be within rights to call the state EMS agency and reporting him.

Second... I35 is nasty. PLEASE make sure you know what's going on when you stop on the freeway - vehicle positioning, safety warnings, don't get nailed by some yahoo on a cell phone. I've wiped out there myself once.

For bulk, I always just run to Galls, but you can probably just google "EMS supplies" or something similar, as Galls can be pricey. Bulk 4x4s are dirt cheap, abd pads are pretty cheap too. Of course, any friends in a FD or hospital help too. Sometimes, Sportsmans Guide has some first aid supplies for cheap.