As you probably realize, the link you provided is a project proposal for crowdfunding, not a shipping product.
For actual products you can purchase, check out the links the author of that proposal provides under "Competition".
If you're on a budget or in a hurry, use an opaque sticker or piece of opaque tape that covers the lens. Then open the Photo Booth app on your Mac to make certain no recognizable images can be transmitted from your iSight camera. If you ever intend to use the iSight camera again, understand that some residue from a sticker or tape might remain on the screen glass over the camera port.