regarding the bolt (I have not bought one or tested this yet) there was another thread here that mentioned the following (
http://www.ptcruiserlinks.com/forum/...erms=horn,bolt )
"...As I recall, it is an M6x20 (metric). You will probably not be able to find a self threading bolt (I couldn't) but you can remove the bolt holding the existing low note horn and use it to thread the hole for the high note horn then the bolt you buy will screw in with no problem..."