I have a pretty much brand new (no signs of use) Jerry Hill Vehicle Mount for sale.
On his website it says he doesn't make them anymore... - I bought this from Jerry two years ago
and have used it about 5 times, but always protected it against scratches or scuffs.
It comes with U-Bolts for Speedrail in various sizes, that were originally included (not in the pictures,
A Zephyr / Scout / Flyer / Pilot Type Female Socket Block (the more sturdy 6-hole version of these)
can be included if your arm is of that type.
Asking USD 700,- with socket block
All the best