I have made one a couple years ago by taking apart a strap springbar and using the small spring that was inside. Got the idea from a thread on wus after losing one on a G that I was doing a battery change on.

A situation where you cant stand it when you know something doesnt work like it should because you lost a small part and are determined to fix it cheaply yourself.

That was about 2 years ago and Ive never used that alarm but I know it works.