I noticed a while ago that they were making changes at the Shun Tak center and it seemed to be more difficult to find shops who sold packages to Macau Saunas, nor could I find any recent intel here. So, I went back yesterday to do some recon. I found 4 shops that sell them. There may be more, but these are the obvious ones.
All shops are on the third floor from the center -> west. One, 325 (the associated picture) is in the center, the other three (306, 308, 309) are next to each other to the west near the escalators on that side of the building. All will have advertisement similar to what you see in the pictures, either on the windows or the walls within the shop. So, if the shops change location within ShunTak, just look for photos on the walls within the shops similar to the picture.
These aren't hidden locations and there is no subtlety in their 'marketing', so I feel no hesitation in listing the shops or posting the picture.