ASUS UX302L Notebook Battery Compatibility

The battery in my laptop has expanded enough to start deforming the bottom cover. I can't seem to find the replacement battery (C31N1306) in stock online. I'm curious if anyone has a reliable replacement shop they trust.

Also, does anyone know why the C31N1339 battery model wouldn't work as a replacement? I believe this was intended for for the UX303 Notebook and ifixit just says it's not compatible but doesn't provide details.