Question
Where the heck can you find parts? My system works fine but the hydraulic actuator valve now leaks and I can't get it to stop.

Answer
Good luck finding parts. As far as I know they haven't made the controllers for 20 years if not more.  What I would suggest is to find your local commercial irrigation supplier---out here in the west we have Ewing Irrigation, John Deere and Horizon.  This is the place where contractors and government agencies buy their supplies.  Check with them--they may have some old parts on the shelf somewhere.  If you cant find any of these, call your local Parks Department and ask them where they buy their irrigation supplies.  
Otherwise, you may have to install an electronic controller.