Hi Henri..A difficult one to find these days if you want an original. Russell Motors have come up with them in response to enquiries on at least two occassions I know of, so are worth a try. Bantam John..though expensive, has the largest stock of original pistons in the UK, so again worth a go...Other than that it's the forum, ebay etc. JP Pistons in Australia and GPN in Italy are 'modern' possibilities, but both tend to make their pistons a bit heavy compared to the original....If the barrel is an 'non linered' type you can use a pre 1954 'long rod' B33 piston as well...This will give a capacity of approx. 640cc-658cc dependant on the size of piston used (std. to +.060"). With a std. B33 piston this will still leave 3 rebores 'in the pot'..A solid copper head gasket opened out to the new bore size is recommended in that case as well....Ian
email (option): Ian Wright