I've heard them called Massage Balls or Reflex balls. I bought two pair - two different sizes from our local Dollar Tree. Their inventory circulates so if there's one in your area they may not have them any longer. It wouldn't hurt to ask - for a BUCK it would certainly be worth your time. Otherwise they seem fairly easy to find on google. I did a search for Chinese Massage Balls. I even added with chimes. I found Marble balls and some Reflex balls for only $6.00 or so plus shipping. Check around, maybe even call a few retailers. If you have a Dollar General or Dollar Tree or some such store for more inexpensive merchandise you just might get lucky and find them.
One example
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