I don't have my calipers handy, but my Wico's are somewhere right between 1-1/2" and 1-9/16".
Watch out for the "wico-style" joystick auctions.
Those are the cheap knock-off ones.
As far as the others go, it's a bit hit-or-miss.
If they say Wico (without the -style) in the title, you're probably OK, but it's hard to tell by the pictures alone.
If you go by that rule though, you will miss alot of auctions that are titled things like "old leafswitch sticks", and "old original joystick", etc...