For best results, purchase the appropriate cartridge from Brother or an authorized reseller. These resellers can be located anywhere in the world but they all get the ink from Brother and should all be labeled appropriately.
What you want to avoid is Generic or Non-Standard ink cartridges made by a 3rd party. This includes refurbished cartridges. The quality control on these items are generally poor and even though they are labeled that they are compatible with the printer, they ofter don't actually work. That of course doesn't mean that you won't get a good cheap cartridge, but it's highly unlikely.
If you go the the Brother Website for this printer and click the "Buy online" button, it will list all of the authorized resellers. Get it from one of these retailers and you won't have any problems.
Hope this helps