NWT Peace Now Ouji Shorts. Bought from original owner who never wore them and I also haven't worn them either. Tried them on and they were unfortunately too big for me.
Suspenders are removable and also adjustable. Pattern is mostly dark gray and white with some red. Buttons on the leg openings are just for show.

Tag says size M. I don't know the exact pair of shorts to find on Lolibrary, but my amateur flat measurements are:
Waist: 14"
Leg Opening: 9"
Suspender length from waist to shoulder: 17"