http://www.partsnmore.com/parts/honda/cb550k/?filters[fitting]=custom
Scroll down about to bottom of page. Right side switch shows a 341 part code (750)k, left side shows 374 part code (550)k
Thinking BOTH switches will fit BOTH bikes w/on-off headlight switch. A little pricey, but at least available, and wire colors look accurate,
and good for when you just don't want to rebuild 'em.