Paint Shaker Ball Bearing Alternative (Mixing)

I needed some metal balls to put in small containers of acrylic craft paint to mix them up. Most colors are fine but the metallics are hard to mix. I needed around 7-8mm sized ball bearings but I only had 4.5mm metal balls (used in BB or air guns here in USA). So I made this holder with a shape that hopefully will make it take somewhat random paths. It holds 3 4.5mm balls and has a male and a female part. Use some super glue or similar to glue the two halves together after inserting the balls.