Watch out for tanks out of China. It's not worth the risk, IMO. I've picked up a used bottle at a decent price from Randy at RL Airguns in the past. You might check to see if he has anything in stock. A fill setup to attach to your rifle may cost an additional $100 to $150 +/-.
Check the classifieds for bottles as well as the used sections on some retailer sites like AoA.
If you end up with an SCBA, the fitting you'll end up looking for is a CGA-347. This may be an option if your local FD will fill your bottle for you or let you fill it after some training on how to use their system. Payment could be in Apples, banana's, and cookies!
DO NOT get an SCBA which has a quick connect nipple as part of the bottle valve system. Trust me on this. It will cost you time, money, and frustration to either get it to work for you or to turn right around and try to sell it off.
What @lenweber2 stated is true. Hydro testing is around $30-$50. Don't skip it. It's a small price to pay for peace of mind and you only have to do it twice. 30 year bottles are becoming available. They run a higher price and, I believe, a higher price for the testing. I'd let the technology grow a little more, and come down a little more in price, before entertaining one of those as an option.
A "High pressure" compressor will fill the tank. A standard home compressor will not. You need something that's going to pressurize to ~4500 psi. Home compressors generally go to about 150psi. An HP compressor runs from a few hundred $ for a lower quality unit out of china all the way up to $2k for something of high quality. It's a tough pill to swallow but, well worth it IMO. I can get all the free air I want from multiple FD's due to my profession. I haven't taken advantage of that benefit in years since I got my own HP compressor. It's incredibly convenient.
Hope this helps!
Tom
