Numrich appears to still have some. Not pmags, but $5 each http://www.gunpartscorp.com/Products/1163650B.htm
In playing around with my shopping cart quantities, they appear to have 3732 of these in stock. "Appear" being the key word. They're rated 3.9 stars out of 5 on MidwayUSA's website by past users.
They tend to be brittle like, I have two that are cracked straight down the back... for 5 bucks cant go worng...
Just checked.... Magazine, 5.56/.223, 20 Round, Black Zytel, Made by Thermold, New This Product is no longer available.
UPDATE....Numrich/Gunparts Corporation now has the 20 round mags available for a "modest" $14.95. See: Magazine, 5.56/.223, 20 Round, Black Zytel, Made by Thermold, New Gun Parts | 1163650B | Numrich Gun Parts
