I've got something like that, except instead of a sled I have everything in a backpack.

I found a cigarette ligher cable that was normally intended for radar detectors for about $2.50 (clearance item at the local radioshack), one of those iRock 300W FM transmitters for portable mp3 players (runs on a pair of AAA's) and a RCA->headphone adapter to tie the whole thing together.

Why would you need a sled and/or PCB? Just more weight to carry around. The only beef I have with the iRock is that there seems to be a bit too much bass in the signal, so I had to add a special EQ setting that cuts about 6db off of the lower frequencies. Oh, and the power button is far too sensitive, so I have to keep a spare set of batteries around.