The Seimitsu LS-32 is a pretty nice joystick for arcade controllers, but there aren't any official octagonal (8-way) restrictor gates, so I made my own! It took a couple of tries, but the latest version fits and works just fine. Get one here!
I ordered an earlier version in both polished alumide and polished blue strong & flexible, and only the alumide fit for some reasons. I stuck with it after that. Also I assume it will have slightly more durability in the long run.