These are kits that contain parts that can be used to manufacture lowers for the AR15. I have no association with this company. I don't know a lot about how a steel lower would work, but this is an option to get a AR before the deadline and it is only $25 for the kit.
http://www.theflatspot.net/ar-15-receiver-flat.html
http://www.theflatspot.net/ar-15-receiver-flat.html