Bear Necessicities should definitely be your first stop if you are looking for Cornell Gear. Their prices substantially cheaper than the Cornell Store or other comparable places. I would definitely start by checking out their selection. Alternatively, look at the Cornell Store and then see if they have the same thing at Bear Necessities.
I have bought stuff at both. Bear Necessities doesn't necessarily have everything that the Cornell Store does, but their selection is pretty big. They have sweatshirts, t-shirts, and other clothing items in addiiton to souvenirs such as cups, posters, etc.
I would definitely recommend stopping by there if you are looking for Cornell gear. The Cornell Store is more expensive so unless you can't find someting at Bear Necessities, I wouldn't necessarily shop there for Cornell stuff.