I just received this link from a USA source,even though the description does mention tyre inflators if you look at the packaging these are certified food grade(for what that's worth),apparently these are what they use across the pond for keg chargers. ;D
http://www.amazon.com/gp/product/B00CMWJV2W?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00
Note: Rather than thread spoiling i made a seperate post on these here,hope that's appropriate admins ? ;D