Hi JJ, welcome!
I've been out of town visiting family to celebrate my MIL's 80th birthday, so haven't been around to check in here until now.
Those pants are AWESOME! I haven't seen an exact pattern for that style, but ITA with Wendy that it shouldn't be too hard to add the ribbon once you have the pants.
Seems like this is a project where you could make the pants yourself and then decorate them, or just start with store-bought pants and embellish.
I would do a long strip of ribbon that fits the circumference of the pant leg (plus 1/2-1"), then lay out & pin on the folded ribbon strips for stitching, with another long strip on top to make a sort of sandwich before attaching. You'd need a lot of pins, that ribbon can be slippery, so watch for gaps between ribbon strips, but I bet they'd be pretty simple to make once you decided on all the different ribbons!
Hope this helps!
Wendy
