Here's the guy's website. It's cheaper on ebay though:
http://www.emiata.com/
I was quoted $450 at a local upholstery shop to sew in a new window, but they said it would require removing the top and cutting out the old window, resulting in the new window being bigger than the old one.
The kit doesn't sound like much more than a copy of some instructions, a roll of clear window vinyl (my guess is 1/16"), some glue, thread and simple tools. I can't imagine that kit costing much more than $30-$40 to put together.
I think i'm going to try it within the next few months or sooner if my window cracks or breaks before then.
-Larez2