I have been going to Leon Tailor for many years and Jhonny has always produced excellent results, often copying a design from a photograph in a magazine with amazing accuracy.
His shop is in the lane running off "Garlic Lane" or Jalan Sahadewa. IF you are running short of time you can email him at jesika_stefania@yahoo.com and attach an image of the garment style you want. You will still need to get a fitting in person of course, but that can be arranged at your hotel if you are in the Kuta-Semiyak area.