I don't know what kind of tools you have available to you, but if you have a drill you can make the spacer from something like a plastic vegetable cutting board. Make an impression on the piece of plastic and drill out the bolt holes and the center hole first. A grinding bit for the drill can be used to rough out the central hole. If you have a small rotary tool, like a dremel that's better yet. Cut the outer shape after the holes are right. It is the holes which need to be accurate, not the outline. Maybe somebody has one for you. I thought I had used mine when I switched over to a speed carb, but didn't. No idea what I did with it, but if I run across it you can have it.
SB