Catherine's and Jessica London carry plus sizes that seem significantly oversized, with extra wide sleeves. They also have extra wide shoes in large sizes. They are both online, affiliated with one another, and with some other sites, including one for swimsuits, Swimsuits For All. In my opinion, Jessica London has better fabric and style, but Catherine's runs seriously big by a size or two, and also has pretty and different selections with thought put into accommodating different types of large bodies. Some of this retailer group, I think Catherine's, offer petite and tall versions as well.
XPlusWear is an online clothing retailer with more hip, more youthful, and exciting choices. It looks like they top out at 5x, which they define as 28 (this varies between retailers). Some of their cuts are very forgiving of fat, so they may still fit, or could be easily altered.
The actual sizes of various clothing retailers online for the same numbered size vary tremendously, as does various styles they carry. I'd always check the size dimensions on each item's page and get as close as you can. In the product description, retailers generally tell you which fabrics are stretchy.
Also think about which fabrics may shrink vs not. Note: Rayon often shrinks a size. Cotton shrinks some. Polyester and acrylic usually do not shrink. But polyester wears hotter.
For higher end shoes, SAS goes big and is supportive, with some types easier to put on for those who are challenged to bend over. Like their buckles actually fasten with lycra. So does an Italian shoe company, Marmi, go into very large sizes. Both have stores too, so you can try them on.
A frustration out there is retailers generally just size up existing designs, which are mostly for the rare (5% of the population) hourglass figures. Or they give us tents and sacs. What we really need is designers designing to enhance the various shapes of obese people, so our sexiness can be displayed, and we can celebrate it! Anyone in the clothing business who wants to take this on?
9 months
