Back in the day before the major CAD sharing sites and manufacturers openly shared their models there was a man named Ed Sparks, who used to personally go through and model each and every component in the Kit of parts.
He made the website
http://www.firstcadlibrary.com/ and it was the gold standard for many years on where to find CAD files. The site's design hasn't changed since it launched but he still adds files from time to time and it serves as a living archive of how much FIRST has changed.
Luckily for you the van door motor has been a staple of FRC for many years and the model is on that site.
Just make sure that you check the model against the version of the motor you have since there have been 2-3 different models over the years with subtle differences.
Thanks Ed for the site, I have used your models countless times over the years.