Where can I find the schematics/CAD model for MacBook Pro's components?
Apple isn't known for making their computer parts user replaceable or making their parts public, because of this I would think it would be highly unlikely Apple would publish CAD files/designs of parts. Here are some possibilities I can think of for finding a CAD file.


Find a patent.
I'm not sure if Apple patented the chassis, but if they did you might be able to find the patent. If you're able to find it you could take the dimensions of it and turn it into a CAD file using a software like Blender, Fusion 360 or any other CAD application.
Contact a third party part manufacturer.
There are multiple third parties that manufacture Apple computer parts. One example of those companies is iFixIt. They provide some parts, kits, and guides for replacing certain computer parts. I took the time to find the parts you need. The bottom chassis is made up of two different parts. The first part is the upper case assembly, the second is the lower case assembly. If you contact them and explain your situation to them, they might provide you with CAD files, this isn't the most likely though.
Using a ruler and CAD software.
You've said you couldn't find any CAD files online so I won't mention that. That leaves one solution. Making your own CAD file, and just so you know, it's probably as complicated and time-consuming as it sounds. It's one thing just to make the part so it looks similar, but it's another thing to make it so it fits.


Good look finding/making the CAD file so you can make this part. I will look for a patent and make an update if I can find one.

P.S. Just so you know the part in the older macs is made out of plastic/rubber and not acrylic.