I have had good luck with Liion Wholesale Batteries.I find their prices to be very competitive.
They have the 17500s, but out of stock on the 16340s. *sigh*...
They look like the best bet, yet, so I'll just keep an eye on them for the 16340s, and hope they'll still have stock in the 17500s when they do.
The 16340s are for other lights that take a single CR123.I'm pretty sure you can't use 3 x 16340's with the standard head ...