Don know if I'm saying something silly as I'm not sure I fully understand what you're after, but...you could use this to connect to the paintball valve:

http://www.ebay.co.uk/itm/Flowfit-BS...item87148ecd74

and this to connect to the co2 nut:
http://www.ebay.co.uk/itm/CO2-to-Argon-Adaptor-/281040858137?pt=LH_DefaultDomain_3&hash=item416f57 2c19