I prefer to buy from dealers that look like they have good business with plenty of parts and good sale record on eBay or just very simple parts.
Where I bought my 836 pistons, the seller was very clear what was included. It was exact as told when I received the parts!
I bought a Flex-Hone (64mm-69 mm bore) for half price and 1/3 shipping cost than most of the other. Hondabond for $8.95US, 15.51 incl shipment to Sweden. All of them small business sites as it looked like.
The shipping cost is important to check when a part can cost very little but huge shipping.
eBay is very good, maybe to good when the shopping cravings attack me! Here in Europe we have eBay.de, eBay.co.uk, and amazon sites in the same way.
All forums give me inspiration too. Now SOHC forum, before Audi forums that gave me good upgrade/tuning/service ideas that delayed my CB750 return with 2 years. Earlier Home Cinema forums that gave me ideas for about $30.000US during 5 years. Possible to order stuff 24/7! :-)