I believe he's looking for brands of flat beds, not trucks.
You did not specify if you need a dump flat or not.
I cannot recommend a specific one, but look on craigslist. I got my utility body off a truck that wan't being parted out but after talking to the guy for a while, I got the guy to do it. I would also suggest an aluminum one, if you can afford it and find one, it will never rust and you'll increase your payload because the bed takes up less of the total weight.