Where can I find Lego x-pod playoff pods for the game? I have some of the original pods but cannot find others, where do I get them? 
I would also need sheets for the things to build and their attacks.
These are no longer in production, so your best bet to find the sets that you are looking for is Bricklink. Here's a list of all the X-Pod sets for sale.

These are the sets that were included in the game:


4348 Aero Pod
4347 Auto Pod
4346 Robo Pod
4349 Wild Pod


For building instructions, I'd recommend the instruction scans on Peeron. Take a look at the X-Pod theme there.

Here are the instructions for the game. See this question for more information on those.