Well, you can capture wild Eevees in Black 2/White 2 early in the game (around the third city, I think). There are hidden evolution stones through the game and from what I've read, you're able to buy more in Black Tower/White Treehollow and Join Avenue (if you care to level it up). There are new type of Eevee evolutions too, but I don't know what their requirements are.
Check this page
out, might help you.