I was told no under wires for at least a month after lumpectomy surgery.
Not that I would have wanted to wear them anyway, too hard on the stitch lines.
I also understand that if you are having lymph nodes out, it becomes important to have your bras professionally fitted to help prevent lymph oedema.
Your surgeons office may have a brochure for the breast care nurse contact, otherwise you can find them yourself and contact them. McGrath Foundation breast care nurse. They should have a listing for one in your area, otherwise ring your surgeons office and ask the receptionist.
They will usually come and visit you in hospital after surgery and as mentioned, will organise the care kit.