Birthstone ring for my mom?

Do you know of any websites that have birthstone rings that can be personalized? I'm looking for quality jewelry like gold, silver, and platinum, that doesn't look tacky. Is that a good idea for a christmas present for my mom? My sister and I are in college and she misses us so I want to get a ring with all of our birthstones on it. Thanks!

www.walmart.com
Personalized and each birthstone can be there of each of you. They are inexpensive too.
And don't look tacky or cheap.