OH, I totally didn't get the whole vest/tank top thing. I was scratching my head, wondering about "stylish" women's vests. Maybe in the 80's... Though the 80's seems to be coming back, so maybe I'm actually behind.
Anyway, to answer the question, the Gap and Banana Republic at the outlets usually have tank tops with built-in bra support. They're not patterned; they're mostly solid colors, though I have seen some striped ones. Those are relatively affordable, though.
Cheers!
Heather W