After shopping around, and worrying about the hassles of getting a TPMS system into Canada without paying outrageous customs and brokerage fees, I ordered the EEZ RV TPMS 515. Their link is at
https://eezrvproducts.com/eezrv-tpms-info
The rear wheels had intermittent connections, so I called up the manufacturer to ask for ideas. They sent me a repeater system to try out. The deal was that I would pay for it if it worked, and otherwise return it. I thought that was really good customer support. The repeater solved my problems.
Reading the instructions for the EEZ RV TPMS and other models like the TST, I believe that there are some standard components used in all of these systems, since they all look alike and have the same setup procedures. So, you should buy from any of these vendors on the basis of price or service, and you'll likely find comparable performance with all systems.
–Gordon