It's a messy and seriously time consuming job to remove the potting to get to the components, but if you can be bothered then it can be done.
As for finding these parts. I have one set left, but in typical Thai fashion, the shop where I got them now says that they don't exist. Erm, I got them from you Sir.......No you didn't......Well this packet just happens to have your shop name on it.........
A chum of mine fitted an inline fuse, as Dave suggests. Worked fine.
Another option is to run a programmable servo controller. I have one and it basically monitors rpm (and the TPS if you want) and controls the servo by reading the output of the potentiometer inside the servo housing. Just like the PGM does. Then you can play with RC valve timing all day.