For people in the UK who don’t want to faff with international shipping, I bought one of these;
They sell them through Ebay for about 80 quid. I like it and the company is small enough to care about what they’re doing; I actually had a chat with the MD about whether it would work for paint and he seems nice.
It does mix VJ paint (and others, of course) really well. I added an elastic band to the top thingy so I can leave the bottle shaking for longer without getting bored. It goes BRRRRRRRRRRRRRRRRRR and the paint is mixed!!
The single drawback of it is the green LED, which is… Mmm. Bright isn’t quite the word. Probably visible from orbit. It’s a device you won’t forget you left on. Nor will people in neighbouring countries.