Base Screw Mount came off Doorbell

The left mounting screw in my doorbell kept spinning. When I was finally able to remove it, it appeared as if the issue was not the mounting screw, but the mounting base. The mounting base was spinning around in the plastic housing.

I able to remove unit off the wall, and I have one mounting screw, and one mounting screw lodged in the base. The doorbell unit also has a large hole on the left side to accommodate the base, but I worry about how secure the device is now that there is one less screw to mount it to the wall.

Please advise. I read somewhere that an individual can theirs replaced.