Hi Jordan,
Welcome to SaleHoo!
I doubt if we can trace a wholesaler willing to customize leggings. This clothing is usually made of spandex or some stretchable material and customizing them with your own design for printing will not be as easy as personalizing prints on paper or on simple cotton shirts. Print designs on a spandex will have to be collaborated with a textile manufacturer and I am sure this does not cover the leggings end product yet.
The most that some retail stores do is to provide options for print designs, with the materials (printed spandex) already available.
Here are wholesale suppliers for leggings in our directory. I filtered my search to those that can send internationally.
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Hope this helps! ;)
Kind regards,