There is a previous
AP discussion thread on this topic; lots of good information there.
One of my Bay Area OC clubmates orienteered in Brazil a few years ago, and yesterday I asked him what he did about the compass situation. He told me he bought one there, and then very kindly insisted that I borrow his since he has no present need for it. In line with some of the comments in the thread referred to above, the bottom of the needle of the this compass has "BR" hand-written on it, presumably for "Brazil".
Finally, another of my clubmates,, who is also headed for Brazil, just ordered a "Southern Hemisphere ME - Brazil" compass
here.