According to the compendium, the information for creating a Hybrid vampire is in Dragon Magazine 402. You can check here and type in vampire hybrid : http://www.wizards.com/dndinsider/compendium/database.aspx

You may also want to see this question: https://rpg.stackexchange.com/questions/36083/is-the-hybrid-vampire-any-good

I personally did not go for a Hybrid when I wanted to make a Vampire character myself, but that was mostly because I didn't want to screw around with making a Hybrid in general, and I found that, for my personal needs, the multi-class Vampire feat had everything I wanted for the Vampire PC I did make.

it seems(from DCShannon's comment) like it might be in 400 instead? I have no idea why it would show up as in 402 and be in 400,... but you could check both at the very worst I guess?