OK, I've been away from Etsy lately while juggling the rest of my life, and maybe something has changed, but....
....even though I can only (theoretically) PURCHASE certified lead-free onesies from, say, Target, the moment I alter them in any way (in my case by dyeing, but embroidery would be similar), I become a manufacturer myself and am liable for the testing all over again, even though I haven't added any lead to lead-free items. The presence of the snaps themselves leaves the onesies off the "exempt" list since they're no long exclusively fabric.
I'm leaving my onesies in my shop (the ones that haven't gone to consignment, anyway) because I'm confident that anyone testing them won't find lead b/c they already ARE lead-free (or the store where I purchased them in is deep doo-doo!), although I've taken anything embellished with fabric paint OUT of my shop; I don't know the phthalate content of the fabric paint and I can't afford to get it tested. :-(