it kinda look like a overall look xD im not a good person with material i am good with sewing though but i have to say the outfit looks self ex-plan-ah-tory hmmmm... :I all i culd actually say is look at her outfit and study it right down to the last piece and cunstruct bit by bit i doubt anything i said made since or wasnt even helpful but i try D:
When life gives you pokemon
GOTTA BEAT DEM ALL D:<!!!
Don't worry about being a noob. Every cosplayer started out as one.
Unfortunately, it's almost impossible to find an EXACT pattern. My best guess would be to find a simple shorts pattern and add the bib and straps onto them. You could do this by cutting one large square for the bib and sewing that to the shorts, then sewing two long thin rectangles onto each side to make the straps. I don't see a zipper on her's. Either she has a zipper on the back or she may have made them out of stretchy material so that they can be pulled on.