I saw a painted rubber one like this last year, when I was looking for Halloween decorations.  I wasn't about to pay $20 for something that looked like it would rip if it was grabbed too hard.  So, I made one!  Here's my result....


http://a626.ac-images.myspacecdn.com/images01/71/l_8b9b5bfdeacf1a1654d2851da38ebee1.jpg

The red lines are just sewn on.

..Pattern...

This is asuming you know a little about using patterns.  I don't know how right this is, I'm that great at writing the patterns out.  But, here's hoping:

You'll need:
Black
Whatever color you want your eye to be (e.x.: blue, green, brown)
White
Red crochet or embroider thread
A needle with an eye big enoug for your thread

Black:
1. (I used a 'Magic Ring') Ch. 2, 5sc in second ch. from hook.  Join with Sl St.  Fo.

Green:
1. 2Sc in each around.  Twice.  Join with Sl St.  Fo.

White:
Join to green.
1. 2Sc in each around.
2 1Sc, 1Sc, 2Sc repeat around.
3. 1Sc, 1Sc, 1Sc, 2Sc repeat around.
4. Dec, 1Sc, 1Sc repeat around.  Twice.  -After this round, do a fitting on your door knob to make sure it fits ok.  I'll be a little smaller when you finish the next step.
5. 1Sc in each around.  Reapeat this round untill it's long enough for your door knob.

You want it to be pretty tight.  It should take a little work to get onto your door knob.  If it's any looser, it'll slide around making it hard to open the door and even come off.  It will also take a few tries to get it on the door knob untill you get used to it.

Good luck.  I hope this works.