We don't really recommend any B2B directories such as Alibaba due to the issue that these types of directories have a variety of suppliers listed within them, some excellent, some not so excellent and some just out right scammers. So while they are great resources for finding suppliers from all over, China especially, you don't ant to make the mistake of focusing on the site itself, like Alibaba, you really have to focus on the suppliers within the site itself.
Now I actually have a wholesale business relationship with a supplier I sourced through Alibaba myself and they are the most customer service focused supplier I have ever worked with and their product quality is world class, so it is possible to find high quality suppliers on these sites, but it's just as easy to find BAD ones if you aren't careful.
Having said that, most would say that Alibaba Express is better than Alibaba itself. Some other similar directories you might look at would be Trade Key, Global Sources, Tradetang and D&H Gate. These are all B2B directories listing individual suppliers and many suppliers will all be on multiple directories. So remember, focus your research on the suppliers within the directory, not on the directory itself and first and foremost, safe payment options should be at the top of your research list. Credit Card is the absolute best, PayPal close behind, things like Western Union or other similar, STAY WELL CLEAR.