Wild Blitzle don't appear in Black2/White2. There are, however, Zebstrika in Route 3 and Route 7. If you want a Blitzle, you'll have to trade/breed for it.
As for getting a different Electric-type Pokemon...if Blitzle isn't an option, try getting a Magnemite from Virbank Complex. Your next best bet would be Emolga (look for rustling grass in Route 6) or trading for an Elekid from Black2.
Either way you go, here's the thing. Flaafy might prove reliable if you give it time, the reward being high Special Attack and a few status moves. Blitzle/Zebstrika, in my opinion, are underrated while having superb Speed and useful Abilities. The Elekid line has huge power and Speed at its disposal. And the Magnemite line has high Special Attack, defenses, and decent Speed on its side. Any one of the Electric lines given can't do you wrong.