WTF is a Juice Bag you say?? Well it's a saddle bag for your bike, with a battery nicely fitted inside and it's connected to a wiring harness.
I know... Sic! It's $857 bucks, you can get it in three styles (Nasty, Sancho and 1/2 & 1/2) and you can snag one from their website.
This is Nash's "Looky Looky" Iron Head Sporty with a black Juice Bag.
Here it is in natural on their "RPG".
Another black Juicer on "Cordano" Evo Sporty. Hopefully you've seen enough examples and won't confuse Nash's Bag with this Juice Bag.