To see what would be involved with a bolt on circuit breaker I picked up a 30 amp today, hot doggies it's made in USA! I'll post a link to my photobucket account since I haven't figured out exactly how to do this right.
One picture shows several sizes of fuse and breakers from a train to the current ones. On my red bike in the end I'll use the small breaker and change terminals to slide ons.
The large breaker is the type we have used for years in commercial vehicles. You can trim it way down by removing the mounting tabs or just one of them and shortening the terminal mount screws sine we are only going to use one ring terminal on each end. I've seen these with so many rings you could barely get the nut on. Just make sure you insulate it with tape or whatever pleases you.
I did find out you have to either drill out the bike's ring terminals or cahnge them to ones that fit the breaker.