Had a similar problem with them trying to get tail dolly tubes. At
that time they stocked several different valve stem types but it took
a few phone calls to sort it out. My spare main tubes came from them
but that was a few years ago.

In an emergency it is fairly easy to modify the stem by cutting it,
sleeving it with brass model tube, and silver soldering. Had to do
that once when I forgot to remove the stem extender.

Probably easier to support your favorite glider parts dealer.

Easier still is replacing the tail dolly tube/wheel with a solid
rubber wheel from Home Depot. It's not TSO'd, but hopefully you'll
never take it with you in flight.

Chip Bearden