Talk to your paintball guys. See where they get their large tanks - The 200 CuFt ones that they fill the little bottles from.$ 45 from a weld shop once a year wouldn't be too bad. Ask your local FD, If you're in a small town they may be helpful and fill a SCBA tank once a month or so.If they seem helpful make sure your bottle is the same as theirs. Also with the paint ball guys someone may own a compressor? Maybe get a paintball - airgun club started and everyone chips in for a compressor? A $3000 compressor devided by 20 guys is only $150 each.
Just my $.02
Al