H4 SU Carburettor for Mk IV 1.5 litre

Hi There,
I’ve just purchased a 1947 Mark IV with a 1.5 litre engine and am looking for a H4 Hi-Top SU to build as a spare. The casting number is 3266.
Can anyone point me in the right direction? I’ve contact Joe Certo and unfortunately he doesn’t have one.
I am located in Sydney, Australia but happy to source worldwide.
Thanks for your assistance.
Kind regards
Bill