Shimano 400 was really low end and mediocre from that era. Suntour had patented technology, so their low end stuff was better. Head to the co-op.
In general, avoid getting parts for a Traveler on eBay. Ebay is best for the one special part you need to complete a project.
Also, check with your LBS (local bike shop). Mine has a few tubs of good parts that have been removed from other bikes. Any part in the tub is $6 at my LBS.
Not all bike shops save old stuff. You need to check around and find the shop(s) that do.