Shouldn't the idiots at the Big Sky LBS be the ones telling YOU what the part # for this item is? THEY are the Giant dealer. You are their hapless hostage customer. That's a rather amazing story. But par for the course. Too many LBS employees don't GET it.
Oh well. In the NY area there would be 10 Giant dealers within a 60 mile radius of your location. Hope they can help you. If they can't PM me and I'll hook you up with a local Giant dealer by me who will probably order it and ship it to you via phone/credit card.
Or call Giant directly and relay your little tale of consumer woe:
Giant Bicycle, Inc
Address: 320 Corporate Dr, Elgin, IL
Phone: (847) 697-3500
Tell them Patentcad sent you.