This power supply is half off right now:

I got one last week to test with Quasar Science tubes in places with no power supply. I ran 4 tubes for 4 hours off of one charge. I ran a Aputure DS1 at 100% for 3 hours on one charge. I know the same thing can be accomplished with V mount batteries, but this is really useful for other things like charging laptops, phones, batteries. It's small too. About the size of a BMCC, adding 2 or 3 inches in length.