If you shoot it alot I found a bulk fill endcap from a QB78 made by Archers Airguns in the US can be substituted for the endcap on the pistol. This means a paintball cylinder or a Sodastream cylinder can be used, you get cheaper shooting and more shots per fill.

Lawrie Armatruda on the BBS is an expert on these pistols and can reseal it for you if necessary more a modest fee.