I'm a cheapskate, my DD had one that she got from school but someone walked off it with it and I didn't want to spend the $ on a new one.
I traced the circumference of a softball out onto some scrap wood, cut it out with a jigsaw then wrapped neon orange duct tape all around it. I made two and fancified one up by rolling up a bit of duct tape on opposite edge sides to simulate seams and then finished covering them duct tape. It gave the feeling of having seams on it.
I used to be skeptic because the motions/actions required to get good spin with a spinner don't quite match what really happens to spin a softball. However, in the last few years I've found that sometimes the cues used to teach a motion, spin or whatever, benefit from exaggeration or aids like the spinner. As much as I've resisted, I may end up getting one and playing around with it.