There's good Masonic symbols on thingiverse. Thought I'd contribute with a high detail version. I included one with and without a background under the square and compass.
Made this as a wall hanger for the shop. You could also size it to your liking and affix it to the back of your vehicle with double sided 3M tape.
In the second picture I printed is at the unedited size of 134mm tall and 114mm wide. I left the brim in the compass handles and the top edge of the square (for those wondering). The other STL version provides the backing under the square and compass. Lastly, for the copy in the second picture I stopped the print 70% of the way through so it's thinner. The first picture and the fifth picture are the same piece. the first picture is my attempt to put model paint to highlight the raised portion.
After printing a great way to highlight the text and image is to take paint of your choosing and brush or use a small roller to apply.
This is art of my own work. Feel free to source back to this thingi file. This is for personal use and not for resale or commercial use.
Also available is a Shriner Plate design:
and a plate that has the mason symbol with writing
"Freemasonry, Faith, Hope, Charity"