I'd encourage you to hang onto some of that ivory, that's a nice piece!
I know a lot of people practice on plastic spoons. That's how I started out too. It's an okay surface but really doesn't feel all that much like ivory, it's almost sort of stretchy in a way. Corian is a very nice material and scrims very much like ivory. I went to the local home improvement store and asked about getting some sample tiles (2x2 inches) for an art project and they were happy to send me home with a handful for free.
-Katherine