You were advised correctly, Norcold 12XX series refrigerator door gaskets are non-replaceable.
Did you perform the dollar bill test before deciding if the gaskets are faulty? Close door on a dollar bill and gently pull it out, it it slides out easily the gasket (magnet strip inside) has lost sealing ability. If resistance is met, the gasket is OK. This must be peformed all the way around each door.
I found a work-around that solved by poor gasket sealing. First I thoroughly washed them with warm soapy water, dried them. Next I used a hair dryer on low heat to warm a short section, then gently pulled the folds apart enough to stick cotton balls in each fold to hold it apart until it cooled.
This it time consuming, but for me it worked.
Some years ago I did find some links to aftermarket gasket sets that might work,
but they would have to be glued on after the OEM gasket was cut away from the door. I did't have the brass to do that, so that's how I arrived at the aforementioned process.
Old Norcold 12xx door seal thread: https://www.irv2.com/forums/f54/sour...ls-412632.html
Universal door gasket sections: https://www.amazon.com/SUPCO-GIDDS-6...ther+stripping
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