Has anyone bothered to tell you you must use aircon frequently to keep it functioning. If you have it turned off most of the time the seals dry out and the refrigerant leaks away. Once that happens - the seals drying out I mean - it's quite unlikely that a regas will hold for long and it's not unussual to find a new compressor is needed. I often found customers with this problem were reluctant to run their air con often enough (I'd say at least once a week for say 15 to 30 minutes) because they didn't need to keep cool in the car. The internal temperature in the car has nothing to do with the air con being active, that's controlled by the heater controls. You can have the air con switched on - so the refrigerant is circulating - but with the heater control set to hot so you are "nice and toasty" inside. It was very common to have folk coming in for a recharge at the beginning of the summer because they'd never had the air con switched on since the start of the summer before and, of course, all the refrigerant was gone. Sometimes they'd get away with a recharge and sometimes not.
Edit. Air con is big business these days so there are many good OE quality options for parts. I'm a little surprised they're having problems sourcing stuff. In my experience you can walk into almost any trade factoring business and get most of the parts for these cars you'd need. Maybe not actually branded FIAT, but very good quality non the less.
PS. So sorry to hear of your troubles. You're most unfortunate. It's not been my experience over many years of running, mainly, Pandas.
