I have a cousin that sell modesty clothes but her RH Basics are all dresses that mostly free size. You may wish to try and enquire on her RH Basics. You check and let them know plus size of yours are in what range (eg : L, XL, XXL) https://instagram.com/rositabyroshussin?igshid=NTc4MTIwNjQ2YQ==
I got my dresses from taobao. cheap and good.