which is not threaded in the axle part of the length and bush the frame bracket.
how lost?
Simply a longer bolt so that it has a portion of unthreaded shaft. If you are turning (having turned) anything, you can make a speciall one-off bolt from a standard 3/8" Allenhead with an unthreaded shaft, turning the 3/8" shaft down to fit the enlarged hole tightly (adjustable reamer, certianly available in the machine shop if you go this far) and then cutting a new thread behind the shaft. Original is 8mm which could present a problem in the States, but even 1/4-20 woud be enuf to hold the bolt. Come to think of it, just straight-forward reaming the U-braket and frame to take a 3/8" bolt would more than suffice and alleviate the necessity of a bushing.
If you wan to go super-sexy tho, the bronze bushing reamed into the frame so that is a snug but turnable fit would be the best bet. Make that busing slightly shorter than the inside measurement of the U-bracket. THe 8mm bolt can remain as is; thighten that up to the ends of the bushing which will be the part that turns in the hole in the frame. Since the U-Bracket is a poor fit, you should fit a
disc spring (Tellerfeder):
or as many as necessary. Of course in this case the center hole of the spring will have to be larger than the bushing. If the Bolt is the axle, only as large as the bolt, of course.
One should space out the side stand with these disc springs from the beginning. That would probably take care of the wobble and wear to start with so that such repairs are not necessary.