OBK has this Regulator that can be used with Co2 Cartridges. Looks kinda cool, it just pops on an you screw the Co2 cartridge into it and set your PSI.
https://www.ontariobeerkegs.com/ProductDetails.asp?ProductCode=PR-regulated-co2-charger&CartID=4
The site mentions 16g cartridges (maybe...