It sounds like it's a dealership and sales person you want to continue to deal with. :)
I haven't given much thought about combat inside a vehicle, but I'd think a good push dagger would work well for security of grip, and the ability to inflict close-quarters damage.
Knife ?, agree push dagger is great yet double edge can be a legal fubar episode.
I use this... Legal in all 50 states. Abrasive to eyes and lungs and delivers the final blow to the skull.... Also marks said aggressor quiet well... There lies Casper the pillsbury dough boy.....lol !
Crazy days we live in buddy .... Stay safe !