That's great! Thanks for sharing and please post a photo once it's installed.
As a 16 yr old my first car was a '68 coupe (not the HCS I have now) and the very first modification I did to it was add a rear defroster. I ordered it out of the JC Whitney catalog and waited 3 weeks for my check to get to them, then the package to be shipped to me (way before internet!) It was a simple motor mounted in the trunk and two defroster hoses up to small round grilles I cut into the package tray. Kind of a cheesy package, but worked well in Colorado when it rained and snowed.
I've always wanted a factory setup, but just never got around to searching for one very hard.