Last year I needed some Barlow winch parts (a shaft somehow managed to go swimming when I rebuilt the winch. I was able to get all the parts I needed here:
HUTTON-ARCO Yacht Winches
Look at 'Service' and 'Spare Parts'.
The prices were great and the parts are perfect. It took a while for delivery. They were good at responding via email.
I don't recall seeing any cotter pins in any winch. If you have another winch, try taking it apart to see the difference between the two.