I found a post by someone who uses an LPL ET-500 enlarging time with LPL 4550 XLG enlarger.
I also found this http://camerashopnbuy.com/et-500-13/
This pedal is used on conjunction with the ET-400 or ET-500...
I would hesitate simply plugging in a pedal with a physically compatible cord into the enlarger...you have no idea what connection voltages are happening in the enlarger connections, etc. to blindly plug in something with no understanding or schematics to view is foolish!