This is weird, but I need your help finding a ball.

KMart used to sell these little massage balls that look like a virus emoji 🦠. About 12cm in diameter, and really hard plastic. They’ve discontinued the product and I’ve bought about 4 similar ones from Amazon but they’re soft rubbery plastic and not what I need.

I need hard plastic, something I can dig my heel into and bring peace to my plantar fasciitis.