I used to get in ebay and use the search to find parts, but their search engine isn't very good. It's much better to use your generic search engine such as Google or Bing outside of ebay. For example, looking for coils for my K1 I was able to find the exact design on what turned out to be Canadian ebay even though it was a US vendor. If you want to restrict the search to ebay, just include ebay along with the terms you use to describe the part. But without it you may find a better vendor who doesn't use ebay.
(i find this idea is also good for Amazon searches where again the internal search is not great.)