Looking for a cheap plus size corset? For PROM please help?

Corset and cheap don't go hand in hand. You won't get the quality, or fit for that matter, with a cheap corset. Also, if it is cheap it's not going to be made with the right materials to be a true corset (ie. not worth the money at all). And one other thing, corsets shape our bodies, but the style of clothes today do not cover the fact that there is a corset and can at times worsen the issue, unlike the Victorian era when clothes were made for a corseted body. Good luck in your search.