You can find suppliers that are safe to buy from through a number channels, including:
The only way to guarantee that a supplier is safe is to take the time required to vet them. Check to make sure they have a physical address, visit the factory (or as for a video tour), pay attention to any red flags for quality issues, and get samples before mass production begins.
If you don't believe you have the time, resources, or expertise to make sure that your supplier is safe to work with, a sourcing specialist, like Kanary, can help.