This is not as small as the dice, but is small enough, cheap and when used in flashing mode, it runs about a month between charges. When mounted upside down on the handle bar, it also stays very nicely out of the way.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Also, if you’re using an out flush mount, you can use the helmet mount it comes with to mount it under the computer as well.