Remember when we all thought the Galaxy Nexus's 4.65" display was enormous? Those days are long gone, but thankfully, Sony will still sell you a flagship with a screen about that large. The Xperia XZ1 Compact, originally priced at $599.99, has dropped to just $449 on eBay with a coupon code. Alternatively, you can grab one from Best Buy for $499.99 and get a free $50 gift card included.
The XZ1 Compact is just a smaller version of the XZ1. Don't get turned off by the 720p resolution; on the 4.6" display, it's perfectly serviceable. Also present are the Snapdragon 835, 4GB of RAM, 32GB of storage with microSD expansion, a 19MP 'Motion Eye' camera with 960fps slow-motion recording, an 8MP selfie-shooter, and a not-insignificant 2700mAh battery. Front-facing speakers, IP68 water resistance, and Android Oreo are here as well. I don't think you can get a smaller phone with better specs that's compatible with US GSM networks.
A reputable eBay seller is selling them for $499 a pop, though that drops to $449 with code PSHOPEARLY at checkout. If you'd prefer to purchase from Best Buy, you can get one for $499.99 with a free $50 gift card that'll never expire. All four colors (Black, Horizon Blue, White Silver, Twilight Pink) are available from both sellers. Check the source links below to pick one of these tiny phones up.