I have a cue that has an alternative ivory butt cap. Be nice to know where you can get a large enuff piece in solid or hollow rod. I've seen the AI in woodworkers forums. The butt cap is actually quite nice.
Masecraft sells both joint and butt size. I am building a segmented handle cue right now that I intended to use Masecrafts alternate ivory for joint, butt cap and all deco-rings. I ordered it in and and made up five butt size deco-rings, one including the butt cap but found it to be very fragile and chips very easily. I ended up making them over out of Aegis.
Dick