Wendel, I have been in business for 12 years and have only needed to replace a VERY small amount. 2 or 3 total so I am not surprised they are not widely available. I just buy a can and take it out. I'll keep the socket from the can for future use.
Check a local lighting store. They may have damaged cans that they will let you take a sensor from.
[This message has been edited by Electricmanscott (edited 01-03-2006).]
