I think there's a guy in Wolfeboro that specializes in flags. He may be able to help you—but in the meantime, some details would be helpful:
• How tall is the pole?
• Is it metal, fiberglass, or wood?
• Is it hollow?
• Is it set in concrete?
• Does it tilt or unscrew from the base?
If it's not really tall, I'd tackle it with a ladder, a boathook which is masking-taped to a straightened coathanger. Tape some light thread to the coathanger, or use a "timber hitch" knot.
Thread the straightened coathanger through the pulley, tear the tape by pulling on the boathook, allow the coathanger to drop, then tape (or tie) a new halyard to the thread, and pull it through the pulley at the top.
Don't pick a windy day to do this!
