I have a handful of rare vintage XL and L dresses for sale right now, I'd be happy to combine shipping costs for you.
This beauty is from the 50's or 60's, made out of black acetate with chiffon overlay and connected chiffon scarf that drapes over the shoulder and flows down the back.
There is a removable rhinestone brooch on the shoulder and the dress zips up the back.
It measures laid flat 20" across the bust pit to pit, 16 1/2" across the waist, 21" across the hips and 41" long.
I did pin it in the back waist for the pictures, since my mannequin is a size small.  The form and drape will stay the same on a larger body.
It is in overall excellent vintage condition and will make a fine addition to any collection.