I need the wheel fixture that mounts the shower doors. They are at least 10 years old. The part is about 3-4 inches long with a wheel at one end the other end is inserted in the door frame then fastened in place through the side of the door with a "headless" screw by an Allen wrench. HELP!! I can't endure any process if it ends in the ability to fix this door. There are 3 doors; one is a mirror. Thank you in advance.

I have installed a great many shower doors and no two manufacturers are alike. Your best bet is to remove the wheel and go to several show rooms that sell shower doors and try to match up with a manufacturer. From what you have said I'd start with Kolher.