Hi @margarete ,
You will need to find an AC / DC adapter with the following specifications. Try local electronic spare parts stores or search online
INPUT - 100-240V AC 60Hz (Depending on where you are in Brazil you could also get a 127V AC 60Hz or a 220V AC 60 Hz Input Type
OUTPUT - 12V DC/ 2A (12 Volts DC 2000mA)
DC CONNECTOR SIZE - 2.1mm The DC output connector plug should be wired as a Positive Centre Tip type connection. An adapter power supply with a positive tip indicates that the centre (tip) of the output plug is positive (+) and the barrel of the output plug is negative (-). Here is an image which shows what to look for to ensure that the adapter's DC Output plug is a Centre positive tip. This picture is usually stamped on to the body of the unit or within the owners manual.
(click on image to enlarge for better viewing).
Hopefully this is of some help.