Hello humble hawaiian, the head is available from 'Rock Solid Engines' in Australia, here.
16:1 compression ratio, very well engineered and machined from aircraft billet aluminium, but $95AU and needs slightly longer studs than standard.
Other than that, it's awesome, but makes the engine a little hard to turn over.
A noticeable power increase throughout the rev range.
They're made for both 48cc and 66cc engines.