OK, I don't do 550's but.... looking online I see this. These are the other bikes that use the same switch/wiring:
CB550 A MOTORCYCLE, JPN, VIN# CB550K-1000001
CB750K3 A MOTORCYCLE, JPN, VIN# CB750-2200001
CB750K4 A MOTORCYCLE, JPN, VIN# CB750-2300001
I also see this "Not Available" meaning from Honda new so you'll have to buy used. With this in mind you can find a #$%*ty switch that has good wiring and mix and match OR find a completely good unit. Put up a request on this site and list these 3 models. Much more likely to find one from a 770 than a 550!
The following is for a 76 CB550K but NOT a 75 and is available new! This is too bad!
PLEASE SELECT THE MODEL YOU WOULD LIKE TO VIEWX.CB360T A MOTORCYCLE, JPN, VIN# CB360-2100001 TO CB360-2123938
CB360T A (76) MOTORCYCLE, JPN, VIN# CB360-2200001
CB400F A MOTORCYCLE, JPN, VIN# CB400F-1000006 TO CB400F-1038492
CB400F A (76) MOTORCYCLE, JPN, VIN# CB400F-2000001 TO CB400F-2008280
CB400F A (77) MOTORCYCLE, JPN, VIN# CB400F-2100001 TO CB400F-2104166
CB550F A MOTORCYCLE, JPN, VIN# CB550F-1109886
CB550F A (76) MOTORCYCLE, JPN, VIN# CB550F-2000003 TO CB550F-2010866
CB550F A (77) MOTORCYCLE, JPN, VIN# CB550F-2100001 TO CB550F-2114871
CB550K A (76) MOTORCYCLE, JPN, VIN# CB550K-1230001
CB750F A MOTORCYCLE, JPN, VIN# CB750F-1000002 TO CB750F-1015054
CB750F A (76) MOTORCYCLE, JPN, VIN# CB750F-2000003 TO CB750F-2022317
CB750K A (76) MOTORCYCLE, JPN, VIN# CB750-2540001 TO CB750-2575894
GL1000 A MOTORCYCLE, JPN, VIN# GL1-1000001 TO GL1-1020183
GL1000 A (76) MOTORCYCLE, JPN, VIN# GL1-2001483 TO GL1-2032613
GL1000LTD A (76) MOTORCYCLE, JPN, VIN# GL1-2035001 TO GL1-2037000
ANYWAY, should you go looking for a replacement be damn sure to take all the pieces (wiring and switch) to match up! AND take this info also. Do not go without or you may be sorry. Breaking yards/junk yards are NOT an exact science!