BCR-2 for 3 Volt Battery Replacement [BCR2] - $17.95 : DCC Hobby Supply, DCC, Digitrax, TCS, NCE, SoundTraxx, QSI, Decoders, Zephyr, Super Chief, Blackstone Models, BLI BlueLine
Amazon.com: SOLARA-USA AC Adapter + 8-ft Power Cord KIT for Shimano Di2 SM- BCR2, Battery Charger [for BT-DN110 & BT-DN110A] & PC-Linkage Device or Rechargeable Bicycle Light or Bluetooth Speaker, WHITE : Cell