No such beast as a one-piece, sorry. Even if there were, you'd still have to refill it and charge it somehow. And if one thing broke down, you'd have to throw out the whole unit rather than just replacing that part.
Disposables are typically cig-sized, cheaply made, with tiny carts. For a moderate vapor (someone replacing a pack-a-day habit with a similar level of vaping), you'd be lucky to get a couple hours out of them. And you're stuck with whatever juice they have in the cart.
It's an extremely expensive way to vape (so expensive that it makes smoking look cheap), and probably not a very pleasurable one.
A mod is an e-cig that takes external batteries. You can get mods that take batteries that will keep going for a couple days before they need recharging. Or you can get a smaller mod that uses a battery that lasts 8 hours or so. Up to you.
And the external batteries are cheap - a few bucks, as opposed to $10 for a 510 battery.
As far as atties... are you cleaning them? I have great luck making atties last. Others don't. Unfortunately it's just "one of those things" about vaping.