First of all your R4 colour is great...
These screws Reidalpine describes are small cross-headed ones and are diagonally places behind the switch, you can locate them with a mirror relatively easily. If they are loose, all is OK, tighten them up.
A common cause, however, is that the switch itself breaks at one or both screw holes because it is made of brittle plastic (bakelite?). Instead of replacing the switch you can fabricate small strips from aluminum sheet screwed to an intact place of the switch with small self tapping screws. In the old days, when beer cans had a "removable" triangular opening, mechanics over here used to repair these switches with that part of the can! (and they enjoyed the beer as a bonus!).
The worst case scenario would be that the frame, part of the instrument panel, where the switch seats, has broken, so the only answer would be to replace the instrument panel... :-(
By the way, did you have any news about that locally made chassis?