I ended up buying the TST 507 kit with the caps from these guys for $220 shipped.
Motor home TPMS SYSTEMS PRESSURE TRACK TIRE PRESSURE MONITORING SYSTEM,TPMS, RV TIRE MONITOR, RV TPMS SYSTEM
The system worked really well on my 24' travel trailer without a repeater on our trip to Tucson and back. Each way I had a time when one of the sensors dropped the connection but it seemed to work again after restarting the receiver. I had my receive sitting in the console of my truck, would probably be better up on the dash but I need to come up with a better solution than the adhesive on the dash. I think it came with a suction cup too so that might be what I do.
99 Mazda Miata SuperMiata #515 - AKA Sparky SOLD
'91 Mariner Blue Miata project AKA Napoleon