It looks like everyone on here just gave you an answer of a direct link or resource. You obviously are looking for the most powerful sources or at least those that may offer something unique. Do you think if there is a public directory its not already over saturated?!

There are a few methods to figuring this out the good ole fashioned tried and true way:

  1. Contact the manufacturer. If you are looking to sell a commoditized brand, something that’s already available, call that manufacturer and ask if you can buy direct. That’s step one. If they say no, ask them who their best distributor is for nationwide selling – that you don’t care about location and are shipping nationwide. You will get your source.
  2. Purchase from the potential competitor. Even if you don’t have a specific product that you want, maybe you have the category. Go on amazon, you can find their top categories and find who has the highest level of ratings (there is also a way to see who the best seller is per category); order from them. Then you can use the label or the sneaky contact of UPS/FedEx (USPS is tough) to figure out where it came from. Call that supplier and open an account.
  3. Join a Facebook group or incubator. That’s where a lot of people talk, mostly on FB groups say for Amazon. They are private so make sure you have something useful to suggest. Its surprising how closed off e-commerce is until you just make a friend. That’s why biz dev always works ;).

Now go find that drop shipper.