we visited costa rica, driving a small, rented suv.

we left our backpack-sized luggage in the back, uncovered, for all to see, with one of these secured to the car seat frame.

? pricey, but secure.

go here

no problems. figured that if someone wanted it bad enough they were going to have to really fight for it - and that there were other, more convenient targets.

they come in numerous styles and sizes.

good luck.