these are billet aluminum and come anodized black. These allow you to run the smartcraft can wire with the plug on the end so you don't have to disssasemble it unlike the factory mercury plastic ones. I have them in stock.

https://madefi.com/shop?olsFocus=false&olsPage=products/mercury-2-dot-5l-and-3l-alien-cowling-billet-rig-tube-adapter

What size and thickness sheets of EPDM are you using from Amazon?

1/8" thick and big enough to make a couple of gaskets. IIRC, they are about 6" X 14".