Over the Range Microwave
You probably mean 36" width x 12.5" depth x 12" height"?
There are a number of 36" wide OTR microwave oven/hood combinations available (see the following link) as well as a mounting kit to install a smaller 30" model in a 36" space.
LINK > 36" OTR Microwaves & Accessories
Unfortunately, most microwaves of that type are in the area of 16-17" height and 14-15" deep. Since there are only 3-4 actual manufacturers of that type of microwave in the whole world which are just rebranded with different brand names, I doubt you'll find much difference in those specifications.
The Appliance Information Site
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