not sure if it helps but just had a look on stein dinse website it is listed but at a hefty 170 euro but it does say its the same as 748 916 996 750ssie 900ssie st2 st4 to 2000 so you could expand your search for those models aswell also the part number is 55240091A you could probably search by part number aswell just had a search and found this Ducati timing pick up sensor 748 916 996 ST4 55240091A (ducatiparts-online.com)
Weather, work and life had got in the road of getting back to fix my bike Anyway got time at the weekend and I can confirm that a Delphi sensor (Part no SS10941) does work, it must be very slightly shorter than the Bosch sensor as it had a slight miss at 8,000rpm, but I removed one of the copper shims (gasket) and that cured it. (the Bosch sensor was in with 2 shims). Thanks for all the replies. (The Delphi sensor was about£30)
