Amazon.com: Golden Power LR920GH Alkaline Button Cell 1.5V Battery Hi-Pro Strongest Leak-Proof Performance,10 Count (Pack of 1) : Health & Household
Remember that coin cell batteries leak from the negative side, which for most game cartridges is facing the PCB, so you might not even see the leakage unless you remove the battery :
Amazon.com: SR621SW Battery 364 621 for Watch Battery 1.5V Button Cell Pack of 10【3-Year Warranty】 : Health & Household
Amazon.com: LiCB 10 Pack LR41 AG3 392 384 Battery,Long-Lasting & Leak-Proof,High Capacity 1.5V LR41 Coin & Button Cell Batteries for Digital Thermometer Ornament Hearing Aid Led Watch : Health & Household