High Mountain State Park is one of the few if not only cross country and snow shoe location in NJ that blows artificial snow as soon as it gets cold enough.
Other than going up there almost any park or course will work for snow shoes and xc skis. You could go to the cross country course at Central Park in Morris Plains or possibly even around the grounds of Morris County College, depending how far you want to go.
I know the golf course around me allows foot and ski traffic once covered in snow. You cuould look for those as options as well.