Panasonic USA makes the CR123s which are branded by Surefire, Everready, Duracell, Rayovac, and Panasonic. Those brands, with USA manufacturing, are the best choice.
If you shop around on the internet you can find these cells down in the $1.50 range or so, when buying a dozen or more. That's your best way to go. I bought a dozen Panasonics last fall for somewhere around $1.50 apiece I believe. Don't remember where, but if you're internet savvy with Google, you will easily find some good sources.
Lithium primary batteries (CR123) are something which is best to avoid off name brands (especially non USA made) and go with the big name brands. As for lithium-ion rechargeables (RCR123 for example) are not manufactured in the USA. AW are considered top of the line, and they're made in China). If you learn about lithium-ion cells and how to use and charge them, they can be safe. If you don't want to invest the time and effort to learn about charging and using li-ions safely, stay away.
With lithium primaries (CR123) if your flashlight just takes one, great. If it takes two... be certain you only use well matched cells! Or you risk venting/fire/explosion when using two cells of notably different charge states. This is serious. Lithium primaries and lithium-ion rechargeables are incredible power sources, but they are to be well respected...
they ain't your grandpa's alkalines!
Here are some good sources with good pricing:
http://www.batterystation.com/cr123a.htm
http://www.batteryjunction.com/pri-cr123a.html