You can't find Eelektrik. You have to evolve a tynamo, which can be found in Chargestone Cave (it only has a 2-8% appearance rate)
Eelektrik does
Eelektrik - Eelektross
level 50
Eelektrik is an Electric type pokemon.
Evolve it using an Thunder Stone.
You can evolve Eelektrik by using a thunderstone.
The only new one to use thunder stone is Eelektrik to Eelektross. Then you have your Pikachu/Raichu and Eevee/Jolteon.
the only way to get it is to level tynamo up to level 39
Eelektrik is #603 in the national pokedex, and it is an Electric type Pokemon.
I would prefer Eelektrik and Eelektross Because they have an immunity to ground (Please correct if I'm wrong, it may be another pokemon, or this is unobtainable in White).
Tynamo evolves into Eelektrik at lv. 39, give it a thunderstone and it evolves into Eelektross.
The new Electric Pokemon introduced in Black and White are: Blitzle & Zebstrika Emolga Joltik & Galvantula Tynamo, Eelektrik, & Eelektross Stunfisk Thundurus Zekrom