It's great to hear that you're interested in selling kid's clothes. This is a great niche with a pretty lucrative market.
When it comes to choosing a US-based supplier, there are a number of dropshipping apps you can choose from. Our most popular dropshipping app is Oberlo. While products on Oberlo are sourced from AliExpress, with many of them shipping from overseas, you can actually choose to filter out products that can be shipped from the United States. Other apps you might want to consider include Spocket and Modalyst, both of which offer children's clothing from US-based suppliers.
You can also choose to create custom products using a variety of print-on-demand apps. With print-on-demand, you can upload your own designs to products like t-shirts, hats, mugs, and more. When a customer purchases a product, the supplier will print it and ship it directly to the customer on your behalf.
Some popular print-on-demand apps include Printful, Printify, and teelaunch. All of these apps offer customizable children's clothing like shirts, sleepers, bodysuits, swimwear, and bibs. They also have suppliers based in the United States. If you have some ideas for custom designs, then print-on-demand might be something worth considering! Like traditional dropshipping, it's another great way to start selling products online without needing to hold any inventory.
As you continue sourcing products and working on your online store, you might want to check out this guide on How to Sell Kids Fashion Online. This guide is actually from Burst, Shopify's in-house stock photography library, where you can download free professional photos to use in your online store. This is definitely a great resource to take advantage of.
Have you considered what kinds of kid's clothes you're wanting to sell? What kind of marketing ideas do you have for your business so far?