The original Nokia 2110 NHE-1XN a variant which is rather hard to find. I have rebuilt the battery in this one out of two dualshock 4 batteries I had laying around. Surprisingly
Akkupack für hama 41007 / Nokia BBH-1H für Nokia 2110 - 6 Volt Akku z
Nokia 2110 Battery Replacement - iFixit Repair Guide
Nokia 2110 Akku Platine Display Ersatzteile in Sachsen - Görlitz | Büro, IT & EDV-Dienstleistungen | eBay Kleinanzeigen ist jetzt Kleinanzeigen
Original GH5781 Phone battery 2350mah 3.8V for nokia phone battery - AliExpress
Nokia 2110 Battery - Phones & Telecommunications - AliExpress
Akkureparatur - Zellentausch - Nokia BBH-1S / BBT-1XV - 6 Volt 700mAh
Nokia 2110 Battery Replacement - iFixit Repair Guide