I bought a used truck, and it came with a safety hammer mounted in it. Because I didn't buy it myself, I can't be 100% sure exactly what make or model it is, but to me it looks like this one that I found on Amazon Canada, and this one from Amazon.com (just a different color).

Unfortunately after a short time a couple of the clips on the mounting plate that it came with broke. I modeled this replacement in Fusion 360 using the original as a guide. The screw holes are spaced exactly as they are in the original, so this should be a direct replacement.

This was printed in Orange Prusament PETG at a 0.2 layer height using a 0.6 nozzle. I also printed one at 0.3 and it turned out fine, so I probably wouldn't bother with a lower layer height than that as I don't really think the extra time is worth it. I strongly recommend against printing it in PLA as it will not last inside a hot car.

Please print it in the orientation shown as lying it flat will make the clips break very easily due to the orientation of the layers. I used tree supports.