Not all women who undergo a mastectomy will want to have reconstructive surgery, but they will still want sexy lingerie options. Times have improved from when mastectomy bras looked like something your great-grandmother would have found too clunky. Victoria's Secret hasn't picked up the trend yet, but there are several other lingerie manufacturers who have, including Playtex, Jodee, and Amoena, which sell all kinds of bras: plunging, lacy, demure, strapless, and sporty.
The local department store might not carry the mastectomy bras, but you should be able to find them in specialty shops (maybe found in the medical center where you were treated). Ordering online is also an option. If you want even more options, some department stores, notably Nordstrom's, will often add prosthesis pockets at little or no charge to any bra you purchase from them.
After your surgery is completed, you doctor will probably advise you to avoid underwire bras, especially if your lymph nodes were removed. This because the wire from the bra can easily jab you in an area that's lost some sensation after surgery, which can cut your skin leaving you open for infection. Avoiding underwire bras can cause some problems for large-breasted women. Some women have found a solution, through purchasing underwire bras sold in maternity stores. These bras often have a short wire, making it extremely unlikely that it will ever poke out or up in the wrong place.