I am a James Perse DEVOTEE! I feel your pain b/c I am always on the hunt for JP goodies.
I see you're in Boston... My Equinox gym's store sells James Perse, so when they have their sales, I always pop in to see what t-shirts may be on sale. Looking at their website, looks like there is a gym in Back Bay and they're building one on Franklin St., so if you live near Back Bay, you should pop in during their summer sale (right now).
It's too bad you didn't post a few weeks ago, b/c Rue La La had a JP sample sale with t-shirts at 50% off. So sorry
I love LNA! They have the best t-shirts and leggings. I've seen Mary-Kate in the v neck tee so many times. Hautelook.com is having a sale on this line tomorrow. They have great deals up to 75% off on some amazing designers.