Nowhere.
They don’t know what they’re selling, and they won’t be able to tell you accurately what you’re buying. Mostly they never see or touch what they sell, they just collect your money and find somplace that claims to have it for sale and have it sent to you. Then it’s good luck or good gosh, it’s the lottery.
To know for sure what you’re buying, buy from someone who will tell you correctly what they are selling because they have held it in their hands and looked inside it.
To my knowledge — that would be
China: http://www.aliexpress.com/store/330416 — see some discussion at 30%-50% discount / Free shipping / Coupon--------Shenzhen Great Wall Technology(Simon) Convoy-Flashlights and Simon’s posts around the place, intermittently (he’s got a youngster and isn’t here as often as, ahem, some of us)
US: MTN Electronics: LEDs - Batteries - Lights - Chargers - Hosts - Drivers - Components - 1-Stop-US Source — see that thread for a whole lot of discussion; RMM has a youngster and a career starting and he’s still here a lot.
I buy stuff from other sources — but that’s gambling, fun if you can afford to lose what you’re risking.