Audelia
If you're anywhere that Amazon.com delivers, my favorite brand can be found there--it has the rather silly name of Heather's Tummy Tamers, and is a combo of peppermint, ginger, and fennel. For plain peppermint oil, I use another one called Pepogest (which I also get through Amazon, but some health food stores carry it too; it's a bit more common than the Heather's).
I've seen similar products under other brand names in the UK and elsewhere, so it shouldn't be too hard to find no matter where you live. Meanwhile, keep drinking that tea, it does help!
Do post back if you do find any crystals that were of use; I'm always willing to try another one.
Thanks for the tip Jolie! I will indeed let you know if I find a crystal that works