I stopped using SlimeAzon about 2 years ago., haven't been to FEMA-Mart - formerly known as WalMart in almost as long - and would never even have a nightmare about buying anything bicycle-related from them, anyway.
Fleabay is ok for some stuff, but I've heard some horror stories about actual engines bought there.
Never had a problem with BikeBerry, they have a lot of stuff, ship fast and customer service is good.
Just put in a small order with Gasbike, they did screw up the last one and their customer service was non-existent, but this order is hard to screw up, we shall see.....
For bicycle parts, I used to go to a local bike shop where they DON'T just try to sell you the latest, greatest and most expensive and have a pretty good stash of little odds and ends for older bikes, but they're having problems, might have to look for a different store.
Yellowjersey.org is very good for older and more unusual parts, Biketiresdirect for mostly tires.