I wouldn't use a garbage bag either. The best ones I have seen were thicker than the one in the video even. I have seen this stuff in stores and cannot remember where.
I use a web belt system that goes on almost like a safety harness for tree stands, but without the lag straps. I drug mine last year with it about 100yds and it was very nice. I had mine in a heavy duty game bag.
This is more the type I would get
http://www.sportsmansguide.com/net/cb/original-deer-sleighr-game-sled.aspx?a=450188. nice thing I see about these is you don't need a heavy game, just something to keep the flies off. The bad thing is the 5lb weight.
This one is polymer 3ft x 6ft, and if you could find the material, and get some solid grommets in it that would do the trick. Remember to tie the actual drag rope to the deer, NOT the bag or else it will rip.
This thing used with the harness would be sweet. On the harnesses, I would get one that goes over BOTH shoulders, buckles in the frong, and has a strap out the lower back to attach to the deer. The ones that use your hands behind your back are hard on your shoulders, and take up both hands. Mine leaves the hands free.
Something like this
Called the Deluxe Deer Drag. That is the one I have.