I had a set made for my Wing (See below). They should be able to hook to about any ball hitch (less the ball) as I've used them on truck's reese hitch. I pick up my hitchless spyder tomorrow. It wont' be hitchless for long. The price isn't for the faint of heart though. I have run these on my Wing at 80+ (with police escort) and never had a problem or ever worry about them.
They are cast and come about in three sections via quick pins.
I bought them in '10 so I'm not sure if they are still making flag poles and mounts.
The contact info is:
M & M Machine Services
P.O. Box 548
Paris, IL. 61944
Ask for Kevin (mmmachine@comwares.net) and let him know your with the PGR.
Note: I buy all my US and military flags from Eagle Mountain flags in Texas (
http://www.eaglemountainflag.com/) as they are made in the USA.