I purchased the Canon PSC900 case which form fits the S90. I also purchased Richard Franiec's custom grip for the S90 and was quite concerned about how the case would handle the grip. In the end after consulting anyone I could find familiar with leather work (not many left) I decided just to force fit the two and see what happened. Seems to be working out just fine. Although tight the camera does still fit into the case and the leather of the case is starting to break-in.
Couple of quick cell phone snaps.