An historical society that runs a library and the
Mennonite Heritage Center in
Harleysville, PA (30 miles NW of Philadelphia). Search under 'MHEP' to find their web site, which does not give their address, but at least includes a telephone number and maps showing where it is.
Their Meetinghouse Shop sells traditional items like redware,
Scherrenschnitte,
Fraktur and also genealogies and local histories.