Here's the products in question.
GRS Trackball: https://www.microcenter.com/product/639681/grs-ts-utb-pro-arcade-trackball
Atari Fightstick: https://www.microcenter.com/product/623130/atari-ultimate-arcade-fightstick-usb-dual-joystick-with-trackball-2-player-game-controller-powered-by-raspberry-pi-3b
Greetings. They aren't the same size so not a direct fit. The trackball included with the Atari kit is 2.5" and the GRS one is listed at 2"
Assuming the buttons are relatively the same size in both photos the Atari ball looks bigger than the GRS one, so no I don't think it will if you're comparing ball to ball. However it does look like you can modify the Atari case to mount the GRS one in it, but then you're going to mess up the logo on the Atari case by doing so. However if you do your own artwork over their case it isn't going to matter anyway, and then it's even more custom as well!
Keep in mind I'm not an employee though and I haven't really handled either ball in person.
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