Steering stem bearing question

Does anyone know where I can get a bottom steering stem bearing for my KZ1000j that is the size 30mm x 52 mm x 16.5? I found a bearing for the upper triple but I need this size to fit my gxsr front end. Or does anyone know if another size (length other than 16.5)bearing will work with a 30 x 52 spec?

These people can help you.

www.allballsracing.com/index.php/

Thank u very much, they have what I need!