That'd be great if you find anything..
I'm in the process of putting together what's needed and have found that "kids" trackballs are the right size(2.25-3"), some are already made transparent/lighted, and yet can be found for 15-20$
If a spinner weren't a must for me(Tempest & Arkanoid are 2 of my alltime favorites ever, it'd be a shame to skip them), i'd just scrap it and keep the ball serial