why did you get a 27" scale in the first place if you're gonna tune that high?
d'addario gets you string all the way up to .70 that won't be a problem. Just order at one of the dealers listed on the site there's plenty for singapore.
as for the high string, octave 4 plus makes those high strings. Plain Steel Strings
Best bet would be to get the lowest + middle 6 + highest.