You'd probably have a better chance finding a spotted unicorn than finding an 80% completed lower. I was having a conversation with my buddy Dave P. the other day and I was explaining that I was perplexed as to why there aren't a bunch of CNC machines cranking out these lowers. The demand for 80% lowers is incredibly high right now, yet no one seems to be making them. Just as a quick update, Ares Armor is still out of stock.
I'm sure you've heard of Kick Starter by now, and as to be expected several other companies have popped up that offer similar crowd funding options. The good people at Rocket Hub have an 80% complete lower deal. Here are the details:
2ND AM ARMS support the 2nd Amendment and we are starting an open-source rapid prototyping shop. We are offering "commemorative" 80% AR15 Lowers to those who support our project (these are not classified as firearms and can be shipped directly to your address). You will also be supporting the Second Amendment and 2% of all funds raised will go to the NRA.
Since the company has met their initial funding goal they are no longer offering the cool guy price of $50 for a lower and a t-shirt. They are however offering a lower level sponsorship which gets you an 80% complete lower for $100. This is still a pretty good deal and they expect to start shipping by mid April 2013. Be sure to get your orders in by the end of the month.