If it is on the Web, it *will* be discovered. Think search engine "cached pages" and page-snapshot thumbnails at "Compete, Inc." and other such sites.
Therefore, the best approach here is to put up the site with "Brazilian-neutral" content, and be done with it.
Other than that, you can "invisibly" rewrite requests from the many and diverse Brazilian IP address ranges to alternate content. But even if this is implemented flawlessly, it *will* be discovered --and easily-- either due to a failure to track the daily changes in IP range allocations, or by a Brazilian company representative at their Tampa, Florida office...
I'd advise "playing it straight" with your potential partner, myself. Perhaps the presence of the product on your new site can be "played to advantage" instead of attempting to 'hide' it. You just can't put something on the Web and try to hide it like this.. It simply can't be done perfectly enough for this situation.