A replacement battery can be found [link|https://www.amazon.com/MPF-Products-AHB622540N01-Replacement-Compatible/dp/B085RF8H6H?crid=26WK960Q1VO8B&dib=eyJ2IjoiMSJ9.BABAD8LzB0P0WzYqazuHCgaJ6dQ7SUgAcJG294wbtNJqQtGlbhyjmnwZd1sBOvStSgAy-rmoL7w4RgYDQAApQbs4zoT54ZokQIdxD54hOpaHR0ChDM0N_7Go1blqhuq28OvwGk7w9nEa9vhcXhVe3d0YDsfu1rnFKvhKXD4oF1DNquS7K_yl0JeXxw14uuFo64J_cdYRUpcG_cX-05TmhQ.GhE7dfmpIaOyQrwrUjxCdbYVjGIDl9MP-XFP8ApI5p4&dib_tag=se&keywords=momentum+2+battery&qid=1732281716&sprefix=momentum+2+batter%2Caps%2C200&sr=8-3|here|new_window=true].
A video showing how to open the headphones up and replace the battery is here. [link|https://youtu.be/9d99NNEgWTQ?si=5pBL9hiA8A7ZKLZg|https://youtu.be/9d99NNEgWTQ?si=5pBL9hiA8A7ZKLZg|new_window=true]
I didn't need to to any modifications because the battery I sourced was the right kind.