Do you know if there are any CAD files (possibly stl) of just the field - without game elements or anything - just the field
Just delete game elements from the given field CAD.
You’ll find .step file downloads of the field on the vexrobotics.com products pages. On the page for each individual product, including the field, there is a tab labeled CAD download. Your CAD software can convert the step files into whatever format you want.
You can’t download a full field with tiles. That’s why I recommend just removing the game elements. Plus the new games all have better STEP files anyway.