Well I know where at least two are, but I dont know if thier for sale.
And if they are how much do you want to spend?
Honestly, the best thing you could do would be to find a good shop, and get one custom built. will probobly cost less than trying to find an original in the end.
And you can set it up for dual webbers. instead of the funny japanese carbs.
Setanta it would be great if you could dig up the cam specs,
any idea what sort of HP it makes? and how much head work it needs?