When I owned a blue Volkswagen (a 1967 beetle, the best model year they ever made) I always kept a couple of spare wire coat hangers, almost more useful than duct tape. One served as my arial and the other was handy to reach in through the slightly open window to catch the button and pull and open the car in case the key was deciding not to work that day. I would go hiking and instead of hiding a spare key somewhere near the car I always hid my folded hangar with my pre-hooked end for opening the door. I never had to tie down the trunk or the engine cover, they worked just fine.