The ones you need are from Borg AKA Your Tire Supply.
Dually KitThey will look like this and come from a company that is the only one now making longer valve stems for Class C Duallys like the Tire man, I have a set from Tire Man that was the original maker of them and have been on my Class C for over 10 years with no leaks or problems. You can Check the pressure on all tires in a matter of minutes.
Valve stemsDO NOT put the braided extenders on, they will leak and if they come loose from their mount on the wheel they will cause a catastrophic air loss.