Please do note that I have the steel wheels so the following could be different.
You need a high pressure valve stem. It will have a metal tube sticking out instead of all rubber. Pretty much any and all tire shops that do light and heavy truck tire service will have them. I got some installed at Walmart because the shop I was at to get tires installed did not have them and I left for a road trip with the old ones. Both rear stems failed. Temps were over 100* in Nevada/Utah when they went.
Walmart replaced them for $3 each plus tax, no labor charge as their computer has no code for charging labor on this service. I had one done in St George UT and the other three done in Montrose, CO. This service was performed with tires bought and installed elsewhere, quite the (pleasant) shock when no labor was charged.
2000 Roadtrek Chevy 200 Versatile(sold)
'98 Safari Trek 2480
'15 Kawasaki Versys650LT
Perfection is a fantasy, though improvement is possible(Wifey).