Trawling ebay I found these anti-vibration dampers 30x 30 x M8 and shore hardness 55° which I think should be alright for the rear bush. They were very cheap at 1.50€ each. The poly and rubber bushes being sold are ~32mm but for an experiment 30mm should be ok.

Cut the ends of at about 5mm to clear the steel insert-the second attempt is much easier

Dress each end with a file

Drill the hole-the last cut with a 10mm reamer having had the bush in the deep freeze overnight. The original bush is 9.7 and a 9.7mm drill is tight even after using a 10mm reamer. A dress with a file gets it just right.

Nice bush and the test in the vice shows that it compresses lovely

Now all we need is some warmer weather for a road test. We have 10" of snow here at the moment.
Happy Christmas all!