I don't have any answers for you, but you might want to email the companies directly and ask. A good source I've found for finding some companies that sell scrubs is http://www.scrubsonline.com...
You might want to take a look at http://www.scrubsonline.com They provide a directory listing several companies that have online scrub catalogs and I did see some vests at some of them when I looked...
You might want to take a look at http://www.basicscrubs.com. They have plus sizes. Also, someone had provided a link here a few weeks ago to http://www.scrubsonline.com, but I can't seem to find it...