Hmmm. That second one sounds more "piezo like" to me.
Perhaps the first one IS mechanical? My Vanagon used to have something like that when the headlights were left on. It was pretty much just a self oscillating relay in a little plastic box. It irritated me so I ripped it out. Might still have that one laying around here too...

Here's the noise my little chime makes.
http://www.weirdstuffwemake.com/swee...es/273-071.mp3

So many noise makers to choose from. I hope you find the one you want.

steve