The .bin you need is in the first post of this topic, posted from edwin.
You need to copy it to the root directory of a usb-flash-drive and plug it to your machine USB-Port A (don´t know if there are thumb drives with mini B out there 
)
Switch your toolhead to a not updated one, take care to plug the cable the right way, turn your machine on:
Touchscreen: START → Not LOCAL, USB → execute the Snapmaker2_V1.12.0.bin