your best bet is to walk into a store like gamestop, walmart, target, etc. and get a charger there. the charger and usb are sold separatly though, which suchs. and on top of that, they're both $15, so you'll be spending a total of $30. you might find the charger cheaper along with the usb online, but i still strongly recommend walking into a store though. that will guarantee quality. hope this helps.
Just a note, although the cord will need to be for the PS Vita the, err, "brick" can be from the PSP Go's charging set. Might save you a few dollars.
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BB has them cheaper now. Less than 20 to get both (original PS Vita usb and charger) I posted the cheaper prices on the forum recently (last couple of weeks.)
You might not find both parts in a BB. Just get whatever you can there, and the other part somewhere else (If you have multiple choices to shop at.)