Here is a nice 2 piece grinder. Or if you want to get a 4 piece, this one is fairly cheap. I would avoid 3 piece grinders though. They are beyond pointless

I have a mini pink version of the sharpstone and I love it! They are great grinders.

I actually bought my Volcano off Amazon but they no longer allow the sale of vaporizers, along with glass. You can get grinders, rollers, papers, and scales from there but that's about it.

If you're looking for a grinder I recommend a Sharpstone, it's Prime eligible and works great. I've had one for two years

http://smile.amazon.com/Authentic-Sharpstone-Herb-Grinder-G2-B/dp/B003U5IXVK/ref=sr_1_1?ie=UTF8&qid=1393728398&sr=8-1&keywords=sharpstone