I went out looking for a canvas. I bought a blank off-white vintage dress at Burcu's Angels in Vancouver BC. It began as a strange satin thing: high-necked, high-backed, too big, with huge wide shoulders. A mystifying slit ran all the way up from the floor to my navel. But it had been beautifully hand-sewn from long single strips of fabric, and had so much excess fabric that it was perfect for cutting down. Not unlike a paper doll's dress.
Doing all the fitting took more skill than I have, so I took it to my friend Miss Bombshell
in Oakland. She cut away the excess fabric, sewed up the centre, gave it a V-back, and put in some boning. I found some matching silk in a fabric store bargain bin, and she sewed that into a sash.
(Remaking dresses is challenging, but here are a couple of Instructables that involved some impressive surgery: Custom Wedding Dress
and Upcycled Dream Wedding Dress & Accessories