Small Request to folks going to London

To folks in the Boston or MA (or elsewhere if you get up here or see me regularly) area who will be travelling to London soon:
If you have time for or are planning on doing any shopping in London, could you get me a couple of jars of Tiptree Greengage jam? I know Fortnum and Mason carries it, but other places probably do, too. It's impossible to get over here, yet oh so delicious. I will pay you back for it in both money and undying gratitude.