I believe the tapered oil pressure switch David_S mentioned fits a /5... At least the one i got from my local vdub guy does.
2002 1150GSA (non-ABS) - 21st C Highway Adventures
1982 R100RS - new rolling project
1980 R80G/S - gearbox still needs attention + & etc
1973 R75/5 - Black Beauty - love @ 1st ride
1972 Ducati Sport - must look at the 'ol girl again soon