Check eBay completed listings, as recommended, and keh.com. Also ask your father-in-law, or maybe someone here knows, if the enlarging timer can be separated from the cold-light head. I don't know how the Zone VI compensating enlarging timer worked, but on my Metrolux compensating timer, there is a probe that is installed in the head, and the timer needs to be plugged into it to work. The Metrolux probe is removable (with tools). I'm not sure about the Zone VI.