I knew the chance was slim, but I thought I would try. I love KPM porcelain and Meissen as well. Good quality stuff.
You need someone who can get to the Ramstein Rathaus. The area "historian" was a guy named Dieter (pronounced Deeter) who loved in Ramstein village by Azur. unfortunately, he died about 5-6 years ago. However, he took pictures starting with WW2 reconstruction of the area. Ramstein Rathaus had it's eye on his pictures and writings for historical value.
Second place is Ramstein has a flea market on the weekends. A lot of antiques go through there, as well as historical information. German is helpful, but the younger crowd of vendors will translate. A lot of grandparents likely worked there.
Third is Landstuhl Rathaus-kaiserslautern, as it would have the business history. Landstuhl archives are a little harder to peruse and have airbags.
The Blarney Stone would be a last ditch effort, though it may be also a hidden gem in this case. It's got it's own storied collection and being across the street from where KPM was doesn't hurt.
But again, you'd need someone local.
Edit:
DeviantArt
This links to my pic of Landstuhl now-ish
The address puts it as housing.
DeviantArt
This is the hillside and some buildings I never got into. It may be that was the old hauptstrasse.