For those looking at the "tower standoff" idea and are having troubles finding the bracket. I suggest an industrial supply manufacturer. We have a Grainger depot here in Tucson. Catalog number 3332 you can have either a straight leg or flared leg and they call it a clamp bracket. From a quick google search there are still plenty of places that know what a standoff bracket is, I found Beverly Manufacturing Company, Harger whom calls them "Tower standoff snap-ins." Another place so calls them "Round Member Standoffs."
I might also suggest as an option butterfly hangers - I was able to find various sizes at my local ace hardware. Unfortunately I didn't get the right size for my bike so I'm still looking for the standoff style bracket. What also may assist in your local searches - I believe they are called tower standoffs, because they are typically used in communication tower setups, so if you know of a place that builds or works on towers best of luck!