You could try a trailer supply place. They might have something that fits - take a sample of what you need with you. I found new rubber bushings for my cab mount shackles at a trailer supply shop.
If you have a friend with a lathe, you could make something up from plastic rod. My friend made some bushings for me from a Delrin rod. Bonus: he did the work while I just had to mix the rum and coke.
I like Kevin's idea. Kevin: is that the same polyester plastic resin that a company like Energy Suspension would use?
https://teamenergysuspension.com/
