I've got a set of 4 NOS 21mm bushings, part number 10030872 I bought a few years ago. I've never installed them. These are extremely hard to find now and I need 12 more of them. I'm aware that some people have used 19mm Energy Suspension bushing by either forcing them on using the clamp or heating the bar so they melt enough to fit.
Personally I don't really like either of these methods, but understand that nothing else is available. That brings me to the point of this post.
I'm going to use the four I have to make a mold and reproduce them in polyurethane. I'll use the same material that I'm going to make the spring seats from. If these come out nice, I'll make them available for sale, at a very reasonable price.