Some people may not be a size 2x or 3x or larger, but still have problems finding clothes or specifically nice formal dresses so here's some advice on that front, which also applies to 2x, 3x, etc.
Consider a bridal shop for a dress for formal night - as in a wedding gown or bridal party dress, they tailor it to fit you. I'm a size 18 on top and a 12 on the bottom and can never fit into any dresses at Jc Penney or other department stores.
I was going to go to David's Bridals (Chicago area) to get a formal dress made/fitted for me ( saw a few on their website that I liked a lot!).
Then I got lucky and found a long halter dress at JC Penney that I ordered online in size 18, which worked for me in the chest area and I had the tailor at my local dry cleaners take the rest of the dress in down the side seams to fit beautifully.
But go to either bridal shops or take a dress you find elsewhere that fits oni top to a tailor.
This would actually work for anyone who can't buy in the stores as they are 2 or more sizes different on top than on the bottom.
There's nothing more beautiful, at any size, than clothes that fit properly!