Uhhh...
So what you're saying is, there's a tiny paint shaker for model paint jars?!
Are you yanking my chain? Oh meee gawd. Truly I am from the dark ages. When did this hobby go nuts?!?!? HAAA! I find that such a product exists as completely astounding a just a bit whacky!
Hey , guess what?! The acrylics that I've swerved into since my local hobby store stopped stocking Polly S brand, has little shaker BBs inside the containers already. Master Reaper brand comes in squeeze bottles with tiny little metal skulls for shakers! I bought some extra containers for mixing that are Master Reaper brand jars and they come with a skull in each one. Gimmicks... luv it.