The idea of plastic would probably work if the wards weren't in your way, but would be a bit touch-and-go in terms of strength.
Plastic bump key? IMO not a chance of working, but never thought about it before so might be wrong
There was some thread about this before that was very similar... if I remember it got locked and deleted.
Brickstrap is my choice, but can be difficult to get hold of depending where you live.