Eyes:
The acrylic felt that I used for the eyes can be purchased at Michaels, Jo-Ann's, AC Moore or any general craft store. You can find it in the kids craft section with the school craft supplies, pipe cleaners, pom-poms, popsicle sticks, etc. They come in small, individual sheets that cost about 25 cents apiece, so I buy plenty in case I need extra!
You can also use real felt if you desire, though I only have experience using the acrylic craft felt. I cut out the general shapes (you can right-click save the image provided at the top of this pattern and print it out and it should print to the correct scale, but it is just as easy to draw it yourself):
I use these scissors to cut out my eyes since they are small and precise. I fold the sheet of felt in half and cut out the general shape of the eye, a bit larger than I want it to be so I can cut it down, refine the shape and make the edges nicer. Folding it in half will give you two pieces that are generally the same shape, then you can cut them down and make them look nicer as I stated before. Do the same with the felt for the pupils.
Because of the bumpy texture of the crochet, I find that it is easier to use fabric glue to apply the eyes rather than sewing them on. The shape of the eye stays more consistent. I like to use Fabri-tac glue... be advised that it dries quickly and is quite permanent, so be careful when gluing your eyes on.