CDSS is probably your best bet. I believe they work with Philadelphia Insurance, and possibly a different broker could obtain a lower price (though CDSS staff know what is important to dance organizations so what they offer is more likely to be appropriate for you). State organizations for nonprofits may have helpful resources. Connecticut's lists endorsed services, including insurance, at:
http://www.ctnonprofits.org/endorsed But you would probably have to join the nonprofit association as well, which reduces any discounts you might get. The Nonprofits Insurance Alliance Group and its affiliate, Alliance of Nonprofits for Insurance, are an option:
https://insurancefornonprofits.org/about/the-nonprofits-insurance-alliance-group/ More expensive than CDSS's, but they offer webinars on insurance and governance issues, and are generally helpful.