I have the UB40's on my Cruiser 1. I used nylon rivets to secure them - no problems in 4 years, except the price. Urethane is not expensive - $100 or more for these parts is not a fair price.
For my Cruiser 2 project. I found a company that makes EPDM rubber extrusions - Pacer. I ordered them from my local auto store and they were only $40. You get 2 pieces that can be trimmed to fit. They are not formed like the UB40's, they are just curved pieces. If you want to get creative with the fit, you can cut notches in the mating flange to make them look sort of like the more expensive ones.