Grey Jedi costume fabric

I am creating a Grey Jedi costume, taking the Grey part literally. I am doing an overall Jedi aesthetic though, feeling that to be more appropriate, with a few Sith influences to show the rogueness of my character(he used to be a Jedi Sentinel). The pants, belt, and boots are relatively easy.....even a headpiece(really just keeping hair out of my eyes) will be a simple matter. However, due the security rules at the event I will be attending(a general Halloween event, but I am using this as a prototype cosplay costume as well), I can't put a tunic over a shirt, and definitely can't wear robes. My solution to this is to take the idea of the false layered look(like you find with t-shirts with the false long sleeves), and sewing the base layer and tunic into one pullover shirt. It will be a little thicker but it works. I am looking for a dark grey fabric that would have that rough Jedi look while taking on a slightly darker look. Are there any types of fabrics that you could recommend for the tunic layer that would still be lightweight enough to be breathable(I will be in warm weather)? My first instinct is some sort of a rough knit fabric. Not as heavy as burlap, but would still have the look I need. Any other suggestions are most welcome.