Well you can get white coveralls from
there all cotton and dye really nice, they also go way up there in size.
As for the vest that is a tricky one. I have no answers for that as I made my own using scrap material I had and just pinned it together like I wanted, then got real material and had someone sew it up.
As for the hiding bulkyness question. Yu can always do what Jango Fett does. his vest comes down to the belt pouches, and the girth goes up over past the navel, you never see any of the belly area. you could probubly even make an extra wide girth belt to support your middle section and give a more sliming appearance.