My battery is 300+ cycles on my iPhone 5s, and it is draining very quickly, even though I do not have much applications running, and not many of them use background app refresh. Where and/or how can I find a decent replacement battery for iPhone 5s?
I would buy an replacement battery for your iPhone 5s from iFixit. They provide also the tools to replace your battery. It's a trustworthy company. Worked with their parts/tools many times.
All iPhone 5s Models (Not iPhone SE, 5 or 5c)
Watt Hours (Wh): 5.92
Capacity: 1558 mAh
Apple Part #: 616-0718, 616-0719, 616-0720, 616-0721, 616-0722, 616-0728
One Year Warranty - This iFixit product is guaranteed to function for one year.
I do not have financial ties with iFixit!
The iPhone 5 has a limit of 800 cycles with its battery. If you are experiencing that, I'd contact Apple Support and have them run a diagnostic test on the iPhone and test the battery.
If they detect any unnormal battery behaviors they'll let you know.
An iPhone backup, and restore should also be a useful tool if you still arent convinced that the battery is ok.