Hrmmm. Sorry then.. that's really the only place I found any meaningful result for.
The only other possible alternative I can think of, might be to find a way to increase the diameter of your rack tubing where you want a multi-clamp by 1/4 inch, then use a Gibraltar-style multiclamp on it. One way to achieve this might be to bolt a 1 1/2" piece of tubing on top of your 1 1/4" tube where needed.