DON'T do this at home!!!!

[bearded bloke]

Try Machinemart first item in this list should be right .. Aluminium 'V' Belt Pulleys - Machine Mart .. before buying a pulley check it is correct for the section of your drivebelt (think yours is a B section)

You could try a search for engineers merchants in your area

[cptncrackoff]

merry tiller belt is normally an A46 belt, a section 46 inch.

[Aberdeenplotter]

have a word with your local mower repair shop. These guys frequently have a stock of second hand parts off machines that have been scrapped or broken up after mechanical breakdown. They will certainly be able to tell you which particular pulley you need