I'm a bit confused why they are saying they do not have the right equipment? As far as I know most, if not all, 5 or 10lb CO2
tanks come with the standard CGA-320 threads on the top. All you need is a compatible regulator to screw onto the tank.
They may not have a regulator that will work for you (or needle valves, bubble counters, etc) but they WILL have a tank that will work. Just ask them what the fitting is on their tanks, I bet it is CGA-320.