OEM....I think.
I'm replacing timing belt, ac belt, valve cover gasket, etc.
http://www.hondaautomotiveparts.com/
You can also try "negotiating" with your local dealer. I've found that many times they will give you a better deal....perhaps matching online pricing. Then its a question of tax vs. shipping.
belts and gaskets do not really need to be OEM parts. OEM belt tensioners and water pumps are sometimes of higher quality, but the belt itself is generally about the same. gates or any big name brand should suffice. gaskets shouldn't really matter, so long as the material is the same.
try rockauto?