I was thinking about this on my way to work this morning, what kind of sound outputs does your DVD player have? Could it be split at all, either RCA or 1/8" stereo? If so I've likely got the splitters, and long cables, that could likely stretch from my truck to yours. So imagine our trucks parked next to each other, sheet in between for the screen, both stereos blasting out the sound... wouldn't be THX but heck... think that'd work?
82 fj40, 99 uzj100, 06 gx470
97 DR650, 05 525EXC, 01 XT225, 09 TTR125, 07 TTR90, 07 CRF50