Theres the link to where I bought the stuff.
ES-22a Enviro-Safe: HomeRefrigerants.com
If you get the home recharge kit, four small cans, your AC in the APU will take two cans and then you will have 2 spares. They also sell the right gauge. I see they changed their webpage since I bought mine, they now say 85lbs on the low side above 100 degrees.
As for your leak, you have to insist that they charge your system up to pressure, and then use a leak probe on it or they won,t do it. If your are under warranty, insist they do a leak probe, and watch them do it. I went through the same crap, they won't check for leaks unless you make them. It could be anywhere, Mine had a cracked evaperator. So when they fixed the leak, I blead out the r-22, put in a can of Leak Seal, and 2 cans of ES-22 and so far so good.