Where can i find the japanese version of brothers from full metal alchemist? (possibly for mp3 download)?

Find it on youtube. Google youtube downloader (like keepvid or something), then copy and paste the URL address of the youtube video. Then download it as an .mp4. Then, open the file, and change the extension to .m4a so that you just have the audio. Some youtube downloaders will let you download the file as an .mp3, so you could probably use that option too.