That mini with a Joye drip atty would be amazing!
I keep my eGo with Phoenix in my front pocket. The Phoenix is slightly larger in diameter than the battery, but it has never cause and issue. But, i'm talking a few mm overhang. I haven't found a tank I like yet, but I also switch flavors like crazy. For $4, that's cheaper than a traditional atty. So, if you break it/it blows, you buy another and paid the same amount as a basic atty. If you're looking for something that is streamlined on the eGo, go with a eGo-T atty (the tank one) and a package of "tanks" for it. Will be streamlined, and you can carry a few flavors with you. The atty is slightly rebuildable, i.e. you can replace the wick.
As for the battery you got, I think it's the same one I have. Mine's a true Joyetech though, but same thing. eGo with mini-USB port on the front for charging while vaping. Got mine in the 900mah rating too. Love it, and have had it since September (with a month or two of no vaping) and it's still kicking strong! Looking back though, I kind of wish I had gotten the 1100mah rating just to get that little bit longer between charges.