the S4 switches (P/N: 60529884) are getting hard to find.
A few years ago it was fairly easy, but always expensive, around the 100$+ mark.
This is because several Ferrari shared the same (Ferrari P/N 134414)
The same is shared with the milano (alfa 75), albeit indicator is orange, might be easier to find?
what people in EU are now doing is locate one from an alfa 155 or 164
which has a lozenge shaped bezel, then swop out the inside contacts (155 P/N: 112560460), if indeed it is the contacts at fault. These are also on the alfa SZ, so SZ people are on the look-out for this type.
But, have you tried cleaning the contacts?
See this great SZ blog (about 1/3 way down, section #49) with some instructions on the internals of the switch: Tech Tips
anyway, no great help, just for info
photo 1: alfa 155
photo 2: alfa 75 (orange)
photo 3: spider S4 and ferrari