Short grain is indeed what's used sushi, but there is actually a difference between short grain rices. One of them is called 'japonica', and as made obvious by its name, is the traditional rice used in Japan. You would use this rice in sushi, although sushi rice also contains salt, vinegar and some other ingredients mixed in with the rice to give it a little bit of flavor.
Here's a recipe on how to prepare sushi rice if you have japonica rice available ->
Japanese Recipe - Sushi Rice - sushi recipe
There are many shops/grocery stores in bigger US/European cities that sell this kind of rice, if you look around. You can find nori (seaweed) at various asian grocery stores in bigger cities as well.