A couple other ideas I've found:

This one can go under the seat, or bolted sideways against either side of the footwell at 3.5in depth

https://www.amazon.com/Homak-HS10036...CustomerImages

EDIT: The above one has bad ratings for security, I'd go with these two choices:
https://www.amazon.com/Stack-QAS-130...k+access++safe
https://www.amazon.com/gp/product/B0...=ATVPDKIKX0DER


This would be awesome to bolted against the center transmission tunnel on its side, nobody would give it a second thought! Not as secure but a nice diversion.



https://www.amazon.com/Trademark-Hom...ol%2Bsafe&th=1

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Have INPA, PA Soft 1.4, fellow members are welcome to come use if you are in the Seattle area!