I tried eBay earlier but ended up getting replicas in most of the cases.
deals with mainly china made products which look fancy but do no last long. Recently came across Flybhp.com and ordered a set of NGK plugs along with K&N filters for my RE Continental.
Received items by Fedex in good packaging. Noticed their price to be cheapest of all marketplaces, so was a little skeptical earlier but was fully satisfied on the service and the money I saved.