I don't think they are out yet, but when they are you should be able to find them at online knifeshops that deal Spyderco knives.
Knifeworks for example has the older t-shirts so I would suspect they will also sell the newer ones when they are out. You can always ask your favourite online/local dealer if they are planning to get them.
Taken from the 2011 catalog:
PSM Mens’ Polo Shirt
Microfiber moisture-wicking fabric is easy care,
breathable, wrinkle resistant and lightweight.
Embroidered Spyderco chest logo.
Doesn't sound like cotton to me, and I highly doubt it'd shrink significantly.