I'd recommend either flicking through the work of historians you've previously enjoyed reading and seeing if anything catches your interest, and browsing archival collections simply to know what's out there. The Women's Library at London School of Economics holds brilliant collections fitting well within your research interests, and their online catalogue contains fairly detailed descriptions. You may also find that the earlier you go in the time period you're interested in, the easier it is to get hold of sources for free online as they come out of copyright.
I'd really advise not getting too caught up on the idea of researching something that's never been done before. At undergraduate level this isn't expected, especially as you don't really get offered the time and resources to do so. Also, once you have a basic idea your supervisor can help you refine your concept and point you in the direction of research avenues. Your research will probably change as you go along!