Try different bridal shops in your area, many also carry bridesmaids dresses too. Or try this site of bought dresses from here and they are great quality and reasonably priced, https://www.simplydresses.com/dresses/styles_and_trends/casual-dresses . You can also try the site rent the runway .. my friends go her bridesmaids dresses from there and the brides were happy not to have to keep the dress they would use again.
I was also going to recommend Azazie! So easy, great quality, and great prices. They have a ton of color options to fit any palette. Bridesmaids can submit their measurements for a custom dress at no additional charge which also cuts down on alteration costs.
I think we're going with Azazie because there are so many options at great prices. They don't have velvet though. I really wanted velvet but Revelry is too expensive and Baltic Born seems to never have plus sizes in stock.
I had a great experience with Revelry! All of my girls dresses are amazing. I can't wait for them to wear them in my wedding. Their customer service was also very responsive and helped me solve any and every issue that popped up! All of the dresses are final sale, so I do recommend doing the home try on option before ordering!