Depends on what you are after, there is Yambits, Wemoto, Heiden, if you want tuning or rebuild then Smedspeed,
I always price up in the States as well as Europe, as quite often it's cheaper even with import duty and postage.
Be very careful if it is pistons you are after to make sure you know what engine/crank you have as there are a lot of US imports with different length rods to Europe around