OK, so I've looked online, and been to our local arcade parts store twice, and I keep coming up empty. Maybe I'm expecting something that isn't possible.
When I think of a 4-way dedicated joystick, I'm thinking that the joystick will only move in a cross pattern, and physically will not move in diagonal directions. Sort of like a gear shift control, that only moves within defined channels. But every 4-way joystick I pick up doesn't work that way, they still let you move the stick to the corners, but no contacts are closed there.
Help!