the rear freewheel sprocket is actually an assembly that holds the brake assembly on the hub.. you won't find it in some bicycle shop. Inside it are some loose ball bearings.. Honda has some parts, but only a few, afaik. Call them or go by the part dept. and look at the microfilm.
and there's a common NTN 6202 wheel bearing to support the wheel back there..
Ask the repair shop if you can come in and look at exactly what they're talking about "so you can track down some parts" or some excuse .. Then "resign" yourself to fixing it yourself and take the bike back home. Or, if they offered to make something you need and can't make or find yourself, get an estimate.
Ebay is a ok source for rear wheels (or entire bikes).. i saw a PA50 rear wheel a week ago.. winning bid was $3.99.. all-inclusive .. gear box, rear variator unit , tire, etc.. couldn't see the right, brake-side so it may not have had a brake or freewheel.