Not my daily driver (yet?), but made a custom dumbphone by getting a Nokia 3310 without a battery or charger and implanting a 2500 mAh Li-Ion cell and a USB-C port (details
ORIGINAL BATTERY NOKIA BL-4UL 1200MAH NOKIA 3310 2017 NEW BATTERY NOKIA LUMIA 225 BATTERY NOKIA BL-4UL NOKIA ASHA 225 | Shopee Malaysia
BATTERY BLC-2 FOR OLD NOKIA PHONE 3310 3330 3410 3510 5510 6800 | eBay
Battery for Nokia 3310 – PhonePartsdb.com
Replacement Battery Batteries For NOKIA 3310 CS NKC2MH
Amazon.com: DDONG Replacement Battery BL-4UL for Nokia 3310 TA-1036, 225 RM-1011 RM-1126 RM-1012 Battery : Cell Phones & Accessories
File:Nokia 3310 grey inside without battery or SIM.jpg - Wikimedia Commons
PolarCell Battery for Nokia 3310 with 1800mAh - buy now!
ORIGINAL ΜΠΑΤΑΡΙΑ ΓΙΑ ΚΙΝΗΤΟ NOKIA 3310 (NEW) - Battery Eshop