haha, I was going to get the black/matte incase slider case today as well only to see that it's sold out
The other thread has a post from someone who spoke to a customer rep at incase and said that it can be anywhere from one to "several" weeks before it goes back up on the incase website.
As for buying it anywhere other than incase, the only place I found it was ebay, and it was more expensive there ($57 after shipping/handling).
Here's the link if you want it that bad
http://cgi.ebay.com/Brand-New-Incas...ryZ20336QQssPageNameZWDVWQQrdZ1QQcmdZViewItem