Lots of accessories do exist which will work not only with the 9000 but also with other Minolta cameras (or even cameras from other manufacturers). While it isn't a goal for this site to list all the stuff that has been made, some things deserve mentioning.
Eyepiece Corrector 1000
In addition to the Minolta 9000's built-in eyepiece adjustment, nine eyepiece correction pieces are also available for further adjustment of the eyepiece. These can be purchased separately and range from -4 to +3 diopters. Correctors snap into the camera's eyepiece frame.
Angle Finder VN
Used when the camera is at an awkward position, the Angle Finder allows you to view the finder at a 90 degree angle. It can be rotated to allow viewing from the top, bottom, and sides. It also has a selectable 2x magnification mode.
The Magnifier enlarges the viewfinder image approximately 2.3 times. This is useful for critical focus applications, for example macro shots.