Picked one up from ebay - new for under £15 - advertised as Guardian V but looks like the original to me. Don't ask me why they used brass rather than chrome - I'm guessing it's because matching brass ego tanks are so common
Thanks - I've got a spare adapter, but again it's chromed and 510 brassed tanks aren't common. Just being fussy over aesthetics. Price was too good to resist (seller had a few so might still have them).