Although bone has been used as a replacement for ivory keytops for
some time now, the problem is that it's very expensive.  Without a doubt
the best key-top material to use to replace old ivory is ivory!Yeah,
yeah, I know that new ivory isn't available anymore, however OLD ivory
is!What you need to do is find the one old technician in your area who
does ivory keyboard restorations.  He will have a stock of many
thousands of pieces of old ivory and will have no trouble matching your
old ones as to size, thickness and color.  While it's possible to sand
or bleach ivory white again, my personal feeling is an ivory keyboard
looks best when it's a pale yellow or cream color.  After all, you
wouldn't want someone to mistake those genuine ivory keytops for
plastic would you?!

Les Smith
lessmith@buffnet.net