I would start by looking at the CO2 Art, GLA, and even Azoo builds. They seem to be the three most frequently named vendors of pre assembled ready to use regulators, with CO2 Art seeming to be the accepted mid point between the other two for price and quality.
Having never used any I can't testify as to the quality but it seems one can't go wrong with the above. I will say I've dealt with CO2 Art customer service team I'm the past who have been responsive.
Also do a search in the forums for these names, quite a bit of information out there. Good luck!
Sent from my XT1095 using Tapatalk