Best strings for Down-tuned acoustic bass?

[smo]

Hi All,

I like to down-tune to C, F, A#, D#.
And no matter what I do, I get fret buzz, even with a high action.
Every set of acoustic bass strings are just way too loose on the neck.

Is there any acoustic bass strings that have a high tension\thick gauge, and will do the down low justice?
I can only find crappy 'light' gauge strings!
The only one that have done the job so far are the Elixir's - but no-one in my city stocks them anymore!

Can anyone help me?
Thanks, Smo

[sir juice]

try a lower gauge 5-string set, then you'd be tuning up a semitone instead of down 4.