Nice link, I think the $129 pricetag makes it kinda rediculous tho.... Too bad they cant just make a cheap unit that is 12v. You can purchase a cheap Magnavox DVD player at Walmart (small unit also) for $29, If you catch a sale, or have a coupon you can score a small inverter for half that cost and have less than $50 in a player you can replace cheaply if it dies on you.
As far as the wiring on the VCR, I never got a chance to work on one of those, I suspect they just switch the 12v power feed to the unit, but I am not shure.
I suppose you could get a cig lighter plug and wire to the feed for the VCR, plug the inverter into it, plug dvd into that, and go. If not may have to run a relay hooked to the ign on feed to switch power to the inverter.
Whatever you do, keep us apprised of your progress as this is something I am not familiar with, thanks....