I don't understand why you would think you need a new device? If it's as simple as replacing a battery, and the battery isn't proprietary and unique to that device, you should find replacements at hardware stores, pharmacies, and the like, maybe even Radio Shack or whatever it's called this week.

It's surprising how many AF sufferers report that they get their worst episode, or their only episodes, when in bed. It must have something to do with compression of the heart itself, or compression of the Vagus nerve...that's my best guess.
It is hard to accept this as a fact, but the truth is that atrial fibrillation won't kill you. You won't die from AF. If untreated, it could lead to heart failure years from now, but that would be your cause of death, not the AF.

See an electrophysiologist about treating your heart's arrhythmia. Medications and monitoring only go so far because it is a progressive disorder...it gets worse over time. Over time, medications will lose their efficacy and potency, and you'll need a different treatment. So, the wisdom is that you should get the condition fixed mechanically as early as you can BEFORE it progresses to a point where a pacemaker is all that's left for you.

Once again, so that you can sleep, and as much as the palpitations are extremely intrusive (believe me, I get it!), you will not die because of atrial fibrillation. But if you want more peace of mind, see an EP right away.