It's been a couple years, but I found r12 manifold gauges on ebay, either the 2 or 3 hose arrangement should allow for adding r12, but you will need the 609 cert. to buy the stuff. The 609 process is simple and just designed to instill the useer with some conscience about the ozone and what you are doing and some personal safety sense.

Unless you just can't find the proper equip, I wouldn't bother trying to find adaptors; You can't use the equip for anything else unless you flush out the bad stuff, "bad" being relative and meaning both are bad exposed to the other; you can't switch back and forth.