If you do a search for "vintage sewing patterns", several sites come up. I know the style your thinking of(a sleeveless wrap-around shift), but you'll have to search through the sites to see what's available for sizes, prices, etc. It can be time consuming, trust me, but you'll probably find what you're looking for.

Ok
I'll try that.
I think this would great for the lifegrauds at the local Y,and for the sauna.