That's a bit of bad news Patrick, especially if you put a lot of work into it befor the penny dropped.
If you are on the Island of Malta as I understand it, all the older cars had the small pinnion to large metal sector plate drive method of window operation, certainly Triumph Heralds had them and the last time I was on holiday in Malta, Heralds were ten a penny. The Austin/Rover Metro have them if you want a newer donor, all pre-electric window Fords have them etc etc. and in your climate any old car by the roadside should be a potential donor.
Good luck with your experiment, and watch out for monkey metal, [Mazac] bearings for the small pinnion, there was a lot of it about in that era.
Regards,
Brian.