I had this tamper made by Les - http://thortamper.com
It's made of Mexican Cocobolo, with a convex Lignum Vitae base.

I ordered it for a 58mm portafilter, and he actually fit it to the double basket that was given to me by another person on the homeroaster email list at sweet marias.

The tamper has a wonderful finish, excellent weighted feel, and helps make great coffee.
If you're remotely serious about your espresso, you owe yourself one of these.