Re: can't find ar15 lower for life if me.
There are lowers for sale out the @$$ all over the place...but as you astutely observed...many "retailers" are out of stock and have no reasonable idea when they'll be back in stock (if ever)!! Get on the PX here on the Hide, BARFCOM EE, GunBroker, etc. You can't blink without running into a lower for sale...just be prepared for the price tags when you find one you want.
Since you seem to be one of the many, MANY thousands of folks who just "gotta have any AR-15 lower receiver RIGHT NOW!!!," then I suggest heading to GunBroker, sorting the auctions for AR lowers by "Buy-it-Now," locating the cheapest lower available, and buying it. Done and done.