It is for safety reasons that the breaker is used instead of a fuse. That way at least the lights will go on and off until you can get off the road. I bet not too many still have an original switch as this used to be fairly common back in the 80s.

 

Run with the head lights off but the parking lights on during the day. After the 35 to 40 minutes do they turn off? Yes check the parking tail lights and dash light, if NO check the Head lights. If Yes you can narrow down further by pulling the individual leads from the switch for example pull "I" for the dash lights. Many times there is a short in the dash."R" for tail lights. etc.