The original link looks like the real deal, but it's a tricky subject: While you can tell the basic builds apart fairly easily, there are many suppliers who box what is obviously not an eGo into boxes with fat Janty logos on them, for example. And of course while you can tell the eGo-class PVs apart, there are copies on the market that mimic the original very well. So the best insurance is to buy from reputable dealers who are know to actually carry what they advertise.
Joye eGo: Silver ring, smoke-coloured button, white light, plain, smooth finish.
Riva: Golden ring, white silicone button, blue light, plain, smooth finish. 100% compatible with eGo parts, slightly different voltage, but really slightly.
JSB vGo: Silver ring, "diamond" button, various light colours, weavy finish, not compatible with eGo cones or chargers. (In my personal opinion: Complete and utter waste of money.)
Hello F016: Bulky body, long white silicone button, blue light, smooth, plain finish. No cones, charger is compatible with eGo. Actually not a bad battery with slightly more voltage than an eGo, but the missing cone is a pity.