I put together my own, very easy to do. Take some 1/2 stock steal/aluminum tubing, cut into 1 8" piece, one 6" piece and one 4 inch piece, sizes can vary depending on application. take a 5/16th bolts and square off in a grinder ( so it fits into the square tubing)and then weld or JB weld the bolt into the tubing. Drill holes on each end of the tubing except the end you mount the bolt on. I drill 1/4 inch holes to accomidate 1/4 inch bolts (might need to ream a little. put them together with a 1 1/2 inch bolts and locking nut and a washer between tubing. on the mount end I use a 1 1/4 inch bolt I thread a wing nut onto the bolt head piece and use a plumbing washer(rubber)on the top side to act as a shock and dynamic cushion. I have tried several using the same concept with old tripod parts and they have worked well.
Let me know and I could send some pictures of the ones I have made.