The biggest issue for me, in any period, is bust support, so this is were I started my research. I found nothing. Then I remembered that, even today, more than 90% of scandinavian women sport an A cup, or less. I then felt a little better about finding nothing.
Feeling better did not solve my problem, so I improvised. By using known methods of rectangular construction, and carefully proportioned gussets and body panels, I came up with a bust supporting shift. The key is to center the fit on the underbust line, then wiggle in and out of it. There is often unintentional comedy in this process, but it works better than sports bra.
At some point I'll upload a nice diagram of the math, as it is much easier to show with pictures.