Platforms like Eloshapes and Rtings have tools for directly comparing different mouse shapes. You can use the developer tools in Chrome to download them and with a file conversion from a site like this one (I just looked a random one up) you can have a workable STL to 3D print and test the shape for yourself or use as a reference for making your own mouse, or whatever else.
I made a a video showing an example if you prefer to see it done that way.
Open whichever site's compare tool
Hit F12 to bring up developer tools
Click over to the Network tab
Load in whichever model you'd like. You'll see some entries populate the Network tab. You want the 3d.glb.gz file that just appeared
Right-click and open in new tab or double click to download it
Head over to your file conversion site. It must to glb.gz to STL
Upload, convert it to STL, and download your new file
Enjoy