I'm assuming when you say "slim" you mean that the body is not deep so that you don't have to reach around the body that far to strum it. If you're primarily used to electric guitars, simply holding an acoustic can seem more than a bit strange.
Triouble is that the slimmer an acoustic body is, the less projection is tends to have. This is why a lot of "acoustic electrics" with slim bodies have built-in electronics - they are pretty much meant to be played primarily while plugged in. Put them (unplugged) in a room with a few regular depth acoustics and they easily get drowned out. Plus the thin body tends to make them sound a little tinnier (again, when unplugged) than the typical acoustic guitar.
If you're looking for a guitar like that, Ovation is a good way to go, as are many of the other suggestions made here.
But I'd like to recommend that you simply try out a regular-sized acoustic for a while. Borrow one from a friend if you have to. Initially it is going to be a strange fit and will feel a little (or even more than a little) weird, but I think that you'll see with even a bit of experience on your part the feel of an acoustiic will be something you can adjust to and even appreciate. Then you can concentrate on getting the best acoustic for your money and then having the electronics added, as Javi ("Nuno"), Jason and Crow have suggested.
Don't forget that acoustics come in many shapes. You may find dreadnaught styles uncomfortable but have better luck with a folk-style or even a mini-jumbo. Here's an article to help you with determining the different body shapes: http://www.guitarnoise.com/lesson/the-shape-of-your-acoustic-guitar/
More to the point, if you find that you truly don't like the feel of a standard acoustic, then you can concentrate on getting a thin-body A/E. But you owe it to yourself to give a regular acoustic a serious try out before you buy.
Hope this helps and good luck!