I just bought an IPV 2S today but don't have any batteries. I was going to buy one at the B&M but didn't really trust the Chinese battery they were trying to sell me for $14. So then aside from buying online since I want to use it today, are there any stores that sell proper 18650's such as a Radio Shack or Batteries Plus Bulbs?
These are all reputable, known good battery suppliers:
Illumination Supply
RTD Vapor
Lighthound
Orbtronic
Battery Junction
Illumination Supply has Samsung 18650 25R, 20 amp, 2500 mAh in stock at $6 a pop. If you need more amps there are still I believe some Sony VTC4 around.
ETA: I see it uses a single battery. At 60 watts a 30 amp battery is the way to go. There are no authentic Sony VTC5 on the market right now AFAIK. I would stick with VTC4, in either a Sony wrapper or an Xtar wrapper. Orbtronic has their SX30, 30 amp, but it's 1600 mAh, probably a VTC3.