you can get SewFree, the same adhesive the big guys use. I'm not sure who is carrying it right now. It will take some monkeying around with jerry rigged irons to get the same results. Keep in that the big guys do a lot of die cutting with templates, to get such clean cuts to meld. It's cool stuff, but I wil tell you this. If you make something with welded seams, you pretty much eliminate the ability to repair or alter it. That stuff simply cannot be undone cleanly.

anyway, here's some links
http://www.bemisworldwide.com/applications/apparel/apparel1.html