I seem to miss certain fly-ins in
my tristate area.

Each state likely has an aviation division in its transportation department.
Start with www.state.xx.us and replace the xx with the 2-letter designator for
your state.

Then fish around for DOT, transportation or aviation...there's likely to be a
search window. No guarantees the state will be keeping track of things like
flyins, but many do try to offer info for the use of pilots.