Rotary encoders for 65XX and 66XX power supplies

Hello,

Does anybody know of a suitable replacement for the optical rotary
encoders that were used on older Agilent/HP 65XX and 66XX power supplies?
These were phased out on the newer generation supplies which use
mechanical types. Agilent no longer has any stock, and advises me to
replace the entire front panel PCB at a cost of $631.00.

I believe that the encoders are part #0960-0822. I have no do***entation
on them. Pictures can be seen here:
http://home.comcast.net/~66gtojayw/Agilent_encoder-1.jpg
http://home.comcast.net/~66gtojayw/Agilent_encoder-2.jpg

Thanks.