The Traveling Gas Shop at Picasso 347 in Shibuya.

Update: As far as what is found at the shop, it doesn’t differ much from the stuff you’re used to seeing elsewhere from GAS (the books and DVDs, as well as tees), but the space is quite nice, especially the wall with their Shoppingbag display (pictured here). I actually really like the bag, and wouldn’t mind getting one, but find it a bit too pricey (around 3000 yen for the smaller version, and 4000 yen for the big one).