Hi, I tried to cross the model number you gave with Avanti and it did not do an exact cross reference.
Usually when a cooler slowly warms up the causes can be
1. The Compressor is not running at full speed or has stopped running
2. The PTC start / run relay / Klixon assy mounted on the Compressor has failed
3. The run capacitor has failed.
4. The temperature control has failed.
If the compressor is running and it is NOT cooling then there is a coolant leak or the coolant system had become blocked usually in the capillary tube area.
The current model numbers for parts are here:
http://www.avantiproducts.com/parts-accessories/current/yes
And the Discontinued model parts are here:
http://www.avantiproducts.com/parts-accessories/current/yes
Just note there are many aftermarket (like part) sources that will be much cheaper than Avanti sourced replacement parts. Most repair techs would advise you to use locally sourced replacement parts.