What Are Pokemon Cartridge Reliable Sources?

OK so I just decided to get the GBA Pokemon games and all of the reviews I read on amazon (Yes, even ones literally by Nintendo), had reviews saying that it was bootleg. So my question is, what are some reliable websites to get the Gen 3 Pokemon games?

@bigfoot21801: I got a bootleg of Ruby on the GBA one time. Well one thing I noticed immediately was the cartridge wasn't the right color.