You won't find mamillare at Victoria's Secret.
"At this period the dress of the matron consisted in general of three articles: the tunica interior, the tunica exterior or stola, and the palla. Beneath the tunica interior there was nothing like the modern brassiere or corset, intended to modify the figure, but a band of soft leather (mamillare) was sometimes passed around the body under the breasts for support (Fig. 146)..."
You can go ahead and try that one at home, but it probably won't be as comfortable as your Hanes Her Way.