How to deal with gender imbalance…

Smile. Do you want to dance or sit out?
Learn to dance the other gender role.
Familiarity breeds acceptance. I dance whatever gender role I feel like at regular dances, and over the last 10 years the contra community in New England has become more accepting of this as more people do it. (despite very occasional clashes)
Our community has a bunch of red ribbons we use to turn ladies into designated gents (could be vice versa, whatever). By formally introducing it this way, (the caller announces “Here are these ribbons, wear them to tell me you’re dancing the gents part”) seems to tell people it’s ok – same gender folks can dance together.
Same concept, but pre-tied open neck ties make the concept obvious without explanation.
Sub-question: some of us don’t believe in neck ties (it “marks” same-sex dancers) – alternatives?
Caller can help here – remind people (esp. if switching is common) that they are dancing “places not faces” i.e. if a woman comes flying at your side in the new set, that’s your new lead. Maybe also more eduation for beginners about structure (i.e. they need to think about the whole dance, not just where they go next)
Callers use leaders and followers language rather than “ladies and gents”
This occasionally gets confusing, but it is nice.
I’ve found that frequently women are more comfortable dancing together than men, particularly older ones – I’m not sure this is something we can completely “fix” since it’s so culturally embedded.