I ordered a couple from the site below. Got them in about 10 days. I called ahead to check availability.
J&T Distributing: AR-15 & Black Rifle Specialists
YMMV. Take care and stay safe.
I ordered some from here:
http://www.indytacticalsupply.com/
He said he has a shipment coming in Wednesday.
Where did they come from? I don't ever remember seeing them before.