I know this has come up here before but I didn't need one then so of course, 
I ignored the discussion.

I use my light probe, (the triangular shaped one that I think I got from 
Independent Living) extensively at work to determine the status of lights on 
an audio control board.  I have two of them but one went down the other day 
and it reminded me that I should have a backup for the backup.  Anyone know 
of an especially good one and where to get it?  Thanks.  lou