I am in a similar situation and I have had good luck at Macy's and other department stores, particularly in the women's section. I need a petite plus size which is also hard to find, but I really like the Jones New York woman brand. Macy's also has coupons in the newspapers sometimes and deals if you get their store credit card.

Good luck and happy shopping!

PS - Nordstrom also has really good service and I know that they usually have a big sale at the end of July.

Talbots has a nice line of plus sized clothing. (I also agree with the previous post re: Macy's) If you wait for their mid-season/end of season sale you can usually get some pretty decent deals. Plus their pieces work nicely as separates so you can mix up the jackets and pants. (I recommend picking a color group and purchasing pieces with that in mind). I am in court nearly every day and have a limited budget for work clothes, as I am a public employee. I stretch the wardrobe by keeping all of my pieces in the black/grey/navy blue color families. I mix it up with a few colorful sweaters or blouses.

You will stretch your dollars if you buy one good black jacket and navy blue jacket. Then add grey, tan and black trousers. You can then add a couple tops and maybe a sweater set. If you keep your basic pieces in one color group it will be easy to add pieces each season. You should be all set where ever you practice.

TLK

It's not just plus sized women with this problem. I have the exact opposite issue: everything hangs off me and makes me look frumpy. My suit selection is minimal since the only size I can wear is in Juniors where you won't find many traditional business suits. In any other section, I don't see size 0 or 2 & 4 is kind of baggy. I figure I'll just have to get a personal tailor in the future (my metabolism is such that I won't gain weight for over 10 years). Meanwhile, I'm fortunate to have a job offer where I won't need to be in a business suit much, if at all.

Just wanted to let you know that this skinny woman shares your pain.

As I've gotten older and fatter the whole suit thing has become increasingly difficult. And where else but here would anyone take my concerns seriously? 

Thanks!