I have a couple Ballistic Advantage receivers. They are the same as Aero's. Was told that Ballistic Advantage makes the receivers for Aero but the dealer could be wrong.
They are related companies so I was told.
http://ballisticadvantage.com/ar15-lower-receiver.html
Have the same nylon tipped upper tension screw. Looks to be in stock, at least when you add them to cart. $85
I like the logo better than Aero's, The A looks like a construction companies logo in Denver, prefer the double flame or double spade or what ever it is.
Per Aero site:
Aero Precision is pleased to announce a new partnership with Ballistic Advantage. As of December 5, 2014, Ballistic Advantage will operate as a majority owned subsidiary of Aero Precision.
This partnership is a key component to our future success and will allow us to provide competitive pricing on a premium selection of over 100 different barrels and firearm components! Our new sister company, Ballistic Advantage, will continue to operate from its facilities and maintain its brand while expanding alongside Aero Precision.