I find it hard to believe that a replacement wheat grain or other type bulb cannot be obtained...
I have a 40+ year old Sansui 5000x receiver that I completely re-lamped so I know they are out there.
As far as the switch, it may be possible to rebuild it. What I don't know is the exact type of switch. Norm or another could definitely help here, but it is not the end of the road I'm sure.