Is it possible to get an alarm which sounds if the catch of my briefcase
is opened while I am out of the room during a meeting?

I use a soft briefcase like this one:
http://www.crouchandfitzgerald.com/i...cts/hs756p.jpg

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My thoughts so far:

When I have to leave my case unattended maybe I could loop a thin
enamelled wire over some part of the catch so that the wire would get
snapped when the catch was undone. It's not a great way and I'm looking
for something better.

Could some sort of window-catch burglar alarm (with a contact and a
magnet or whatever) be used?

Inside the case I would need a portable but loud alarm sounder which
would respond to a broken circuit. Are there any off-the-shelf products
which would do this?