I haven't looked yet, but in case you haven't already I would cross post this question in the "Spridget" (Healey Sprite/MG Midget) section. You would probably get more responses that way.
With that out of the way, have you looked into Moss Motors, Victoria British, Brittek, or any of the other 'usual suspects' for these bushing kits? I assume "Energy Suspension" bushings are polyurethane. Does it have to be made by them or would a comparable product work as well? If something comparable will work, I'm sure all of the major suppliers sell poly bushes for Midgets.