Amazon has some good ones. Not sure if their what your looking for though.
http://www.amazon.com/PSP-Go-Soft-Carrying-Case-Sony/dp/B002N4TQXI
I have the traveler's case for my GO. http://www.futureshop.ca/catalog/proddetail.asp?sku_id=0665000FS10130985&catid=22444&logon=&langid=EN#
Hope I...