I had a similar problem with a McCulloch and went to MachineMart 0115 966 2900 MachineMart.co.uk
it took a lot of explaining EXACTLY what was needed - I even had to find the manual on a website and copy the images showing the squared ended flexidrive and emailed that to them Then I got the part and all sorted in 10 minutes!!
AndrewCT, April 2010