I am told you can get the plate that you attach the bag too and then attach the whole lot to the tripod comes from a company called centre point. I have googled it but cant find it...... any suggestions?
I took an Ultimate Tripod and modified it a bit.
Here's what to do if you have one:
First off, scrape off the plastic covering on the inside of the pivot point, the part that's connected to the legs. Then replace the tiny threaded rod with a larger one. Throw away that piece of crap plastic knob that's used to tighten the top. I replaced mine with a piece of steel that I put threads into. The more force you apply the less it moves. Then replace the short aluminum rails with longer ones. I modified the front rest to accept the head of a bench rest set up.
On this one I used a cheapo Midway top. Sometimes I put the head of my good rest in it.