Just bought a mountain bike  'Planet' strut pump with a 400 psi gage and the no-leak fitting from REI ... but don't know the diameter of the piston so i don;t know if I can actually push 400-pounds worth... will settle for a little over 300.  Will see tomorrow.  Did this after spending a few hours on the internet looking at paintball sites and calling stores... none of which had anything that would work for less than $200., and that without the N2.  (We're in the boonies in Southern Illinois.)
Terrence
L235/320 N211AL