Shameless plug: I make several of these brackets, and also make custom parts as well - go to jerryholway.com to find the most recent part and price list.
Most of the brackets mount on rods, but a few mount to a long dovetail...
here's one of them that expands for different width rod mounting:
I preordered and received RIGHT AFTER a move with NBA players. Man I wish I had this on that movie. It's a great tool, and I used it on some POV work for the new Halloween coming out this year. Well made, Charles.