I installed a Nest Hello doorbell this week and then designed and 3D-printed the mounting plate that mounts to the existing outlet box in the wall, covers the screw holes in the stucco the old doorbell used and provides mounting holes for the doorbell itself. I love that I can design and make something totally custom in a few hours with a 3D printer.
Troy & Gay 
Great solution! Any chance you’d be willing to sell me one?
I doubt it’d work for you unless you have a small (very old) electrical box like I do because the screw holes are aligned with the screw holes in the electrical box. Old electrical boxes are much smaller than today’s standard boxes. I just posted the Fusion 360 file and the STL file on Thingiverse (https://www.thingiverse.com/thing:2861911) so you can download and modify it to fit yours.
Love your doorbell plate for ur nest…can i buy one…i have older home too…
You don’t need to pay me and it’d cost more for me to ship it to you than it would be to print it. I posted all the files you need to print one yourself. Do you know anyone with a 3D printer or have a local 3D printing shop? They can print one for pennies. Or try an online 3D printing service like Shapeways (https://www.shapeways.com/).