They may also be able to give you some seeds. You just spread them over some dirt (doesn't need to be deep -- maybe two inches) lightly spread dirt on top. Water. Cover the whole pot or dish or whatever with celophane and put in a window. In about a week you will have grass. It needs a little water.

The reason I suggest growing it from seed is that it doesn't last long (at least in my experience.) The kits from Petco have everything you need -- seed, growing container, et al, but are a bit pricey.