Sorry - I just saw this threas.
Columbia has several choices of goretex-like waterproof jackets in women's plus sizes. I haven't tried to find bibs, but they might have pants.
You can go to the Columbia web site, but several other sites carry Columbia, including Cabella's, REI, and the discount sites Altrec and Campmor.
From a fellow/former plus size who's already lost 2 sizes since moving aboard, good luck!
s/v Baja Beagle
"Time flies like an arrow, fruit flies like a banana." -Groucho Marx