You'll have a hard time finding a flat fingerboard, but you also don't really want one. I know, I know, you are used to it and all that, but the thing is that an electric is a very different thing. Steel strings, such as on an electric, take more and different kinds of pressure to fret, so you will find that a classical style neck (flat and wide) is very uncomfortable.
Now, all that being said, you will probably want a wider and flater fingerboard than most electric players. Try to find something with a 1 3/4 to 1 7/8 inch nut, and a 20 inch radius. ESP, Jackson, Ibanez, and other similar companies will all have many guitars with necks along those lines.
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