How far from those cities are you willing to travel? To help you find a good konyoku (mixed bath), I would suggest you to use this online searching tool on our onsen web site : http://www.secret-japan.com/onsen/search/search.php
You can select "mixed bath" and "display on map" or "display list" to get the result. Each bath is rated following several factors, including a grade called "Modesty": the higher that grade, the more women-friendly the bath is; if you look for a rating or 5 or even 4, you should find something suitable...
If you have some travel time, I would recommend you to check Kurokawa onsen, in Kyushu. Link : http://www.secret-japan.com/forum/kurokawa-onsen-%28kumamoto-ken%29-t601.html
. There are amazing mixed baths there, and some of them are really my favorite.
Alternatively, and closer to Tokyo, is located Takaragawa Onsen - http://www.secret-japan.com/forum/takaragawa-onsen-%28gunma-ken%29-t5.html
- which is the largest bath in Japan, and is very women-friendly.