[NSAID]

2013 Moto X here, too. I recently replaced the battery and it's been great to get through a full day again, but I'm nervous about the day when this thing actually dies. I'm looking for something with those 3 requirements as well, and it's incredible how few options there are.

[coldpie]

The Pixel 5" meets the requirements, but it's still out of stock and $750(!). Otherwise the iPhone (same price) is the only other stock-OS, decent spec, <= 5" phone I'm aware of.

[shuntress]

I have pretty much the same requirements (Stock-OS, Decent Specs, Not Huge).

With no love for apple, I recommend (from personal experience) buying an iPhone SE.

Edit: I mention the SE specifically because it is not the same price. $400 vs $750