you could try a scrappy?
btw. i had my air-con recharged yesterday. i spoke to the guy about the older R12 stuff and he showed me a little kit they sell to convert. like a poster said above its basically 2 valves and some oil.
a little more information about costs for what i did etc here under yesterdays date >
http://www.golfgtiforum.co.uk/index.php?topic=20658.msg187799#msg187799