Tim,
I have checked the sizes of the postwar clutch springs - they are :- Outer, 1 7/16" long x .780"dia x .093"wire, 7½turns wound RH. Inner, 1 7/16" long x .530"dia x .066"wire, 10 turns wound LH.
You could try Lee Springs at Wokingham, Berks. - they have a good selection of all sorts of springs on their website.
Regards,
Eddie.