That's great thanks, CR/CRF looks to be the closest match, YZ/WR/KX/RM all have the hose coming off the front which I don't think would be an issue in use but prefer to get it as close as possible.
Read a few reports of the Honda MC using their own developed piston compared to the others which helps.
Ive found a few Honda MC on Ebay but some of them have 1/2 cast into them so I suspect would be no better than my current one. Any idea what year Honda went to 11mm?