Acquiring Insurance is not a fun thing, especially if you start looking in the wrong places.
Places to start looking
Assuming your organization is a non-profit, you have certain resources at your disposal. One such resource is the National Council of Nonprofit Associations which different state-level Nonprofit Associations belong too. Ask them who they would recommend.
The chances of finding an insurance company that is familiar with community bicycle organizations is slim, so finding one that is familiar with nonprofits in general is the better approach. Ask other local nonprofits who they use too.
What to Cover
At least a million dollars in coverage.
Child Molestation Coverage
Does your organization work with kids? You should have child molestation coverage. Sounds horrible, but the act of one rogue volunteer can sink your organization. This would cover you in such an event and require you to do background checks on all your volunteers.