Facebook has a Charlie Benante Fan page that let's you know when some stuff becomes available on Charlies's website. You can check the website periodically if you don't do facebook:
http://www.charliebenante.com/Store/
He recently posted about the 20 drumheads used on WM and they sold in one day! Says he's going to put another batch up soon.
Since they are shipped out randomly, I sent his webmaster (also merch handler) an email hinting if I could have the white snare drumhead and he responded by saying Charlie couldn't believe they sold so fast and said he would make sure I got the white one.:Smokedev: