ACFT RECEIVED MINOR DAMAGE AS A RESULT OF AN ELECTRICAL FIRE IN-FLIGHT WHILE IN CRUISE AT 9,000' MSL. THE PLT STATED THAT HE OBSERVED SMOKE EMANATING FROM THE C.B. PANEL MOUNTED ON THE LEFT SIDE WALL OF THE COCKPIT AND THAT SEVERAL C.B.'S POPPED AND HE LOST THE MAJORITY OF THE ELEC SYS. HE ELECTED TO EXECUTE A PRECAUTIONARY LANDING AT A NEARBY ARPT. FIRE AND HEAT DAMAGE WAS LIMITED TO THE LEFT SIDE ELEC PANEL, PRIMARILY ON THE UPPER C.B. PANEL. TWO SUSPECT AREAS WERE IDENTIFIED AS POSSIBLE POINTS OF ORIGIN FOR THE FIRE. ONE WAS A BURNED UP RESISTOR ON THE TRIM COWL FLAP INDICATORS WHICH HAD A DISCONNECTED WIRE TO A DIODE. THE OTHER WAS A BUS BAR LINK THAT WAS INSTALLED BACKWARDS AND HAD COME INTO CONTACT WITH A FUSELAGE BULKHEAD AND SHORTED OUT. A CONCLUSIVE DETERMINATION AS TO WHICH CAUSED THE INCIDENT FIRE COULD NOT BE MADE.