I think the "best" extentions are likely those by duallyvalve
Dually valve kits for Motor-homes, Busses and 6-wheeled chassis
They are the kind you need a tire shop to install by removing the tire from the rim.
although I never got around to getting them. I planned for a long time to do it, though.
My braided hose extensions from the factory leaked, and I pulled them off after much grief.
I modified my wheel simulators trying to get access. Better, but not a fix
I bought some rigid valve extensions from ebay, along with some rubber insert stabilizers form duallyvalve. Better, but they didn't play well with my TST sensors. The valve stem (push wire inside the extensions) was a bit too long, and would either damage the sensor, plug the sensor, ar just plain not work sometimes.
I eventually decided that these wheel simulators were the cause of all my grief. They may look pretty, but not pretty enough to offset all the headaches they give me....so mine are currently stored in my attic. Honestly, I wish I'd done this years ago!