Hi Janos, just tried a search on ebay using the words "kodak dc215 serial cable" and four results came up. They seem reasonably priced. Check it out:
serial cables on ebay linky (the first one for US$8.95 and the third one for US$8.88 seem to have the best shipping rate).
They seem to be going for around about $25 here in australia (just typed the same search in google) so the ebay prices are just a little less including shipping.
Hope that is what you are looking for.