I don't have that particular type of unit, nor have I worked on one, but, without a remote sensor (usually used for "zone" monitoring on large RV's), I would have to guess that the sensor is probably in your thermostat mounted on the wall... If anyone knows for sure, please chime in :?:
Most likely it is contained internally to the Comfort Control Center (the thermostat). I'm not sure if it is a serviceable piece or you have to replace the entire thermostat. Dometic would be my first "port of call" to find out:
For RV products
Customer Support Center
P.O. Box 490
Elkhart, IN 46515
Phone: 1-800-544-4881
CustomerSupportCenter@DometicUSA.com
If it is in the thermostat, they may be able to FedEx one to you or if you are really desperate, you may be able to get a replacement locally or substitute a different thermostat from Wally World, etc... If it is part of the compressor control module (in the ceiling harness), then it would be a different matter...may be user serviceable, may require a professional (or semi-pro handyman) to be able to locate, remove and replace the part...
Sorry I can't be of more help, but, anything else I could or would tell you would just be a WAG...