I too had this same problem and my temporary fix was to switch the bright and normal headlamp wires going to the foot switch. Thus I had regular lights but hitting the foot switch would make them go black instead of high beams.

So a year or two later I took apart the switch by drilling out one side of the rivets that hold the housing together. If I remember correctly I drilled them out so that they would still align the two halves together when reassembled, then the mounting screws held everything tight. Well first thing I did was clean the corroded and pitted contacts and I reinstalled it, still no go.

Upon taking it apart a second time and checking it with a volt meter I found that the brass rivets holding the brass parts together were not providing a good electrical connection. My solution was wire brushing the rivets really good to try to clean the area under the rivet heads, then I peened the rivet heads good and tight. Now the switch works good as new without spending any money.