I got this from an Alesis representative:
If you need Alesis replacement parts, contact our parts team by calling 401-658-3131 Ext. 1403, or you may also email them at parts@inmusicbrands.com.
I couldn't find a black 8" mesh head anywhere. I contacted them and got one right away at a decent price. I'm glad I did that because I really like these Alesis heads.
Sorry I can't be more help. Try emailing them, though. They might have some answers for you.