answered about 7 months ago by grubby
Try Hào Nam street (off Đê La Thanh west of Tôn Dức Thắng) - there are a dozen musical instrument shops along that street and I noticed that many of them sell music books and such. I wasn't looking for sheet music so I can't tell you more than that.
If you find any good resources be sure to enter them on the site :)