I obtained a rear mudguard to the same dimension as the original on my 1930 TT Rep from them (http://www.auto-cycle.co.uk) ; cost £70.
They require the width/depth and overall length of the mudguard and, of course, the diameter required.
To obtain the necessary diameter, I placed a block of wood on top of the rear tyre and took a measurement from the c/l of the wheel spindle to the top of the bolck of wood.
You will have to cut out a section to acomodate the chain/guard.
Chris.
