@disq@mmccarthy Not the group head gasket (already found these in my google-ings) there is a seal where the spout of the portafilter screws on, wondered if this was a 'standard' size before i get my calipers out.
There shouldn't be any pressure at the spout, so any o ring that can fit snugly over the threaded section should suffice I'd have thought. Surprised it leaks to be honest. Have you tried removing it and just doing the thread up tight?
Googling "portafilter spout gasket" seems to give plenty results, short of finding an OEM replacement, surely a food/temp safe one that's the right size should be fine.
@disq @mmccarthy Not the group head gasket (already found these in my google-ings) there is a seal where the spout of the portafilter screws on, wondered if this was a 'standard' size before i get my calipers out.