I have the same challenge...and am experimenting a bit...I just installed a kit from www.frostfighter.com. I they're the only source of aftermarket electric replacement defrosters I was able to come up with. I'm already troubleshooting it as all elements didn't work BUT that was my installation mistake-- I messed up making the connection to the bus bar. I can say it was very tedious to install...small hands would've been a benefit working in tight places.

Installing it I elected to scrape off all of the existing defroster wired with a single edge razor blade, clean the window with acetone and then proceeded to individually layover the new defroster wire in the same position the old one was so the window would look right. Like I say...tedious.

Doing it over I would likely look for a new rear window...if I'm successful in getting the thing working 100% I'll post a step by step. Just wanted to give you something to consider...