Most fridge models ARE much rarer than most regular ones. Either you you don't get out to enough radio rich places (like radio collector swap meets), or you are in a region where they did not sell well.
A brands presence in an a geographical area is proportional to their representation among local merchants, and their relative sales compared to other brands. Good case studies are Packard Bell, and Andrea brands. Packard Bell was a west coast brand, and they are very common in California and surrounding states, but once you get out towards the Midwest they are very rare to find in the wild (I've only ever seen two of their later offerings in person here, and none prior to the last 5 years). Andrea was an east coast brand IIRC and most of their offerings show up there. Even big national brands like Zenith and Philco have regions and pockets where they outsold all the other brands 10-1 or other brands outsold them by that amount.
Go to the big nationally attended radio swap meets like ARCI's Radiofest, MARC's Extravaganza, or Kutztown regularly for a few years if you want a good feel for what brands are out there and how common they are.