I need to build a better mouse trap

[Peaches]

I'm having a heck of a problem with field mice getting into my car. I've already spent several hundred dollars replacing the AC filter that they like living in, they've somehow gotten bird food stored into my overhead inside light plate, they've taken Kleenex and shredded it for their nest, and I actually watched one run across the passenger side floorboard the other day.

This means WAR!

So far I've:

Put out pellets. I had to duct tape the tray to the driveway under the car because I was worried another critter would get hold of it. They eat tray after tray after tray - nothing.

Put the "human" traps out. They figured out if you turn it upside down, the flap opens and they got some peanut butter and crackers that night for dinner.

Put out the snapping kill traps (I'm getting desperate....). The peanut butter was gone, the trap was snapped - no mouse.

My cat would die w/in minutes if I put her outside. She's old and has never been outdoors. And my dogs of course, are the same so I can't put any of them on sentry duty.

Any brilliant ideas?