Every surgeon undertaking breast surgery has their own routine for post op dressings. We want our patients to be comfortable and to have light compression which assists healing but not tight pressure which can damage tissue or skin (through cutting off its circulation leading to necrosis). Don't forget you might have numb spots postop for awhile which can be damaged without you being aware of that.
In my practice, we use bulky paper pads on the wound which absorb ooze or spots, under a simple elastic 'boob tube vest" made of tubigrip. Not elegant but extremely practical and usually very comfortable.
At the first office visit postop, the dressings are changed to simple clean tape. From that time, a few days postop, our patients can go into a soft bra of any type - we recommend they use a cheap sports bra, a crop top or a maternity bra. The problem in advising you is that one product does not fit all patients, so we don't pre purchase - we wait and advise at the first office visit.
You don't say how many days postop you are, but if more than a week or so should be able to go into a cheap crop top or bra of any type. Look for something both comfortable and that isn't too loose or too tight. And that will do fine.
You'll throw it away in a month or two as your swelling comes down and your shape improves, so make sure it's inexpensive.
And call your surgeon or his office nurse on Monday to check with them before proceeding. They will advise on this all the time. They migh have particular advice, or much as I've provided for you here. Follow their advice.
Good luck.