Hmm. You're right. Sorry, I should have looked closer before linking.
This may work: http://www.impactguns.com/ar15-lowers.aspx
It appears they may have two lowers available, both over $300, though.
I got 3 emails in two days from Delton saying their lowers were available for 120.00. Sold out before I could finish the order. Slick Guns had PSA lowers for 119.00 in-stock. They sold out within 30 minutes. But things are becoming available. I’m sure I can get one for under 150.