Been Googling a bit, and it seems PCP Air Rifles commonly utilise Scuba
tanks, and you can actually get hand pumps that will provide up to 250 bar.
If you are young and fit enough.

http://www.airgunbuyer.com/Showprodu...SubCat=pump s








And here's a small tank.
http://www.stealthunter.co.uk/mini-c...nit-1269-p.asp


Quite an expensive way to get compressed air, though!




Gareth.