RiteBrew currently has some great prices for CO2 Manifolds.
All have integrated check valves and either 5/16″ barbs (fits 1/4″ and 5/16″ ID tubing) or 1/4″ MFL connections. 2 to 8 way manifolds are available starting at just $19.49.
Check out the Full Lineup
Also from RiteBrew:
Perlick Forward Sealing, Stainless Steel 630SS Faucet.