hel1,
Based on your last post, I would approach the Air/Defence Adviser at the Singapore High Commission and explain your problem to him. it might just be ....
Another possible line, which you may have already pursued, is to talk with the Keeper of Exhibits at the RAF Museum. Besides complete aircraft, there are several sites where items are held and - although it will have moved - there used to be something called 'The Reserve Collection'. No: 6 Site at the former RAF supply depot at Stafford is, I believe, still home to a significant collection of items.
Have you tried the museum at Old Sarum? This now houses what used to be the Boscombe Down collection. I was there about 18 months ago but cannot recall any rotary stuff. Finally, and again you've probably already tried every angle on the Westlands approach, could it be that another aviation museum (Manchester?) might have large Belvedere bits.
Depending on how you intend to display the aircraft, can I suggest something which you might think shows I've lost my marbles. If the front of the aircraft is shown with the covers on, is it feasible to fabricate those elements of the front which remain exposed? It wouldn't necessarily have the strength to support blades but it might permit a reasonable representation to be achieved for display purposes.
Old Duffer