Nobody's yet found the "right" fabric for the vest as of yet, sadly enough. Tackle twill is a popular choice due to it's sheen and weave, but its far too stiff and heavy to achieve the correct look. Plus there's evidence that some vests were made of different fabric than others.
Just one thing. I've seen that in 501st crl for Boba it seems that tackle Twill is the most "canon" choice for the material, so that's why I was looking for thus kind of material... Am I getting wrong then?