I also highly recommend Dae's site qualitychinagoods.com for R123A batteries and charger. His latest Protected R123A cells are thinner than his older versions (I have both) and will fit in many lights that previously could not fit protected cells.
I also highly recommend MarkCM's site e-lectronics.net . Again, great prices and service. He's very responsive and will help you out. I purchased 14500s and 17500s from.
And, I also recommend AW. Great service also. I purchased the DSD charger from him because I wanted the aluminum spacers he provides with them (I use them for other purposes along with using them in the charger).
Overall, Dae has the best prices on Protected R123As when shipping is accounted for. MarkCM has the best prices on the other cells. And I prefer AW's DSD charger. All are great sellers tho.