Joined: Oct 2004
Posts: 2,947
Likes: 1
From: Absecon, NJ
Bikes: Puch Luzern, Puch Mistral SLE, Bianchi Pista, Motobecane Grand Touring, Austro-Daimler Ultima, Legnano, Raleigh MountainTour, Cannondale SM600
Harris Cyclery has Suntour & Shimano freewheels ranging from $20 - $50 US. NOS freewheels can be found aplenty on ebay too.
I'd double check that your not getting chain & cog slippage first. Closely examine the cogs for signs of wear. Have you noticed if it's skipping on more than one cog?
You could also try lubing the freewheel body. My favorite is Phil Wood oil for freewheels.