Project on Radio Test Equipment Calibration - Help needed!

Hi - I have a unique request but I am hoping you all can help me out!

I am doing research on the different companies that offer repair and calibration services for two way radio testing equipment. For example, calibration services for the Motorola R2600 series communication systems analyzers. A couple examples of companies I have found are:

Auburn Metrology Lab
Cardinal Electronics

I was wondering if there are any large companies that are the well-known, go-to company for calibration and repairs, or if there are mostly smaller companies like the two above?

Also, if anyone works in the first responder industry (police, fire, ambulance, etc.), who do you all use for test equipment calibration? It seems like this would be a big opportunity for a company who offers these services.

Thanks in advance and I hope someone can help me out!