these (larger) gyros seem like they are much cheaper than the solid state ones. I was wondering if perhaps you could find a source other than canibalizing old gyration products.
http://www.gyration.com/en-US/GyroTech.html
Another interesting thing I have been meaning to do is pull the chip/ccd out of an optical mouse. you can get all sorts of neat diagnostic info out of them, including the raw CCD image of the surface. you could make your mouse scan whatever it is moving over, or place it at the bottom of a sumo-bot to get perfect feedback on your current location and how much your wheels are slipping and what direction you are being pushed…