I use "ProTec" brand cases for my keyboards and am very happy with them. Hard foam core frame, rugged yet lightweight. Highly recommended.

ProTec Web Address: http://www.ptcases.com/

Call ProTec at (800) 325-3455. I somehow remember that they have a custom case specifically made for the Yamaha PSR9000.

Protec does not sell directly to the end user but they can tell you which custom case model # is appropriate for you keyboard and refer you to a local dealer in your area.

Good luck,

- Scott