Go to your local AirGas or welding supply for CO2. Get a siphon tank. Pick up a fill station at PPS on POG Weekend
or order/make one. They are basic. Get a digital fish scale... good to go.
For HPA... buy your SCUBA tanks online. I got mine off ebay for $175 shipped. Brand new and manufactured the month
I received it. BRAND NEW.
From here: LUXFER 80 CU.FT. NEW ALUMINUM SCUBA TANK FREE SHIPPING - eBay (item 130207340727 end time Mar-25-08 18:48:10 PDT)
For filling the SCUBA... tell the dive shop it's for paintball. They might overlook the certs. If not... fire house or welding supply may do it or have an answer.
I can show you my HPA/SCUBA and CO2 filling setups at POG Weekend if you're interested.