Greetings esoares:
I know from personal experience
that, at least a few years ago, both Agilent in
Loveland, CO, and Narda in Happauge, NY, had equipment
to make PIM measurements.
Agilent used equipment
designed and manufactured by Summitek in Colorado
(https://www.summitekinstruments.com/).
Narda (https://www.nardamicrowave.com/east/)
had a custom in-house setup.
I do not have
names for contacting either company, but you could
just try calling the main phone numbers and ask.
You might also try contacting Summitek to see if
they can either do the testing or recommend a test
facility.