There are a variety of online vendors like Alibaba.com, Ali Express, globalSources.com, Oberlo, etc.

Once you search the potential vendor for your products, send them an email or give them a call to have a conversation about the products you are interested in.

If possible try to establish a face-to-face conversation with vendors through Skype or WeChat conversation.

The conversation should be on the following things:

1. You must seem to be a serious eCommerce seller that builds trust in the distributors

2. Most importantly, check the quality of products and price. Maybe you get a better distributor/vendor who could sell you products of good quality at a low-cost price.

3. Know the vendors at a personal level and check for their inventory and supply capabilities.

Moreover, you should meet the vendor personally to confirm and move things ahead of doing good business.