Bob, for posterity, if you go here:
https://www.whiteline.com.au/catsize_bush.php
and click on the "D" and "O" bushings, #4 and #10, and then choose any Parameter and choose "All Sizes" that will show all the Whiteline bushings of that particular shape. Are there any bushings there that match the proportions of the ERA rack? Whiteline makes some very nice poly bushings.