On this I am practically an expert. Walmart tends to have the largest, and least expensive plus size workout clothes around. They carry their regular lines up to a size 20 and a plus size line in 1X, 2X, and 3X. I have never had good luck with Target's plus sized line, but more power to anyone who does. Lane Bryant comes out with one or two cute pieces per year, but they are more expensive than Target or Walmart. Fashion Bug also comes out with a couple of cute pieces per year. You can also try Avenue (or avenue.com) who carries a couple of cute pieces per season.
Junonia specializes in plus size women's activewear. The great thing about Junonia is they use a plus size sloper to make their patterns. A sloper is the basic pattern that a company works off of. Most companies make their sloper for a size 4 and just add a little here and there as the sizes increase. What I never understood is how a clothing manufacturer could have no concept that the proportions of a womans body from a size 4 to a size 20 are not linear.
steps off soap box
Junonia is really the place to go for good fitting clothes for a variety of activities they are more practical than cute.
Another option is to find someone who sews who can make the clothes. Jalie, a Canadian activewear pattern maker, hands down makes the best activewear patterns around. They are multisized to contain every size from childrens to roughly a size 22. While making activewear sounds really very complicated it is like a parlor trick, it is exceedingly easy. I can make a workout top or pants in an hour. They are only a couple of pieces and if you get really cool fabric (spandexhouse.com) you can use the same pattern over and over and everyone thinks you are a genius.
As you can see I have way to much experience on this particular topic, and maybe a bit too much passion. I always felt that the plus size market for workout clothes was pitifully underserved.
stoppping before I jump back on my soap box.
Good luck to your mother.
Shayne
