Solar Chargers

I have a home-made lock for locking things to the roof (or outside) of a car, made originally for windsurfing gear.

get a long length of plastic coated cable, maybe 1/4"

Two wooden blocks, and drill two holes side by side in each.

When the cable end is threaded in one hole of a block and back out the other, you can't pull the cable through; it binds. Use one at each
end of the cable.

You run the cable through your possessions, drop the two blocks in the car door, slam it shut and lock it. No one can pull the cable
out the car dor seal due to the jammed blocks. You could probably just tie a big old knot in the cable and slam that in the car.

Adjustable and can be as long as you want. But it requires something to run the cable through the possessions or a really tight tie-off.

All you need is enough to keep an honest man honest. The casual thief (included judgment impaired grabber) typically will not pause
for a second to cut, break or undo anything.