I saw your comment! Do you have a print design in mind already and a repeatable file?
If so there are a number of great fabric printers out there depending on your print size, color, placement, etc.
If you're looking for a way to develop the legging product you have in your mind with this custom print, I would suggest to check out nabld.com
We are a production platform that helps you design and digitize the unique products you want to sell and connects you with a network of vetted, no minimum manufacturers to produce your product on-demand sustainably and ethically in the USA. You'll be able to find an amazing supplier partner to produce items you WANT to sell.
We integrate through Shopify so you can choose to sell pre-order or in small inventory runs and batch orders to put into production with your manufacturing partner.
If you have questions or would like to share more about the type of product you're looking for, I would suggest setting up a demo with our team at nabld.com!