This is such an easy project, and can be completed with scrap material and elastic. Thankfully I always save the random sizes of elastic that get snipped away for waistbands and what not, so I had everything on hand.
Here's how to make one for your little pirate. I should add, another request has been put in for a pink pirate eye patch - I think I can manage that ;)
Gather your supplies. I used a scrap of thin elastic - to get the right length, I put it around my son's head where the eye patch would be and subtracted an inch. I cut out a 3x3ish square (you can use any size you want really, just make sure it's big enough to cover the eye) of scrap batting (you could also use felt, an old towel, fleece or any other thick and soft fabric). I also cut out two 3x3ish pieces of black quilting weight fabric. You will also need coordinating thread, scissors and a machine (you could do this by hand quickly too I'm sure).
These directions assume a 1/4" seam allowance.
You should have something like the photo above.
Position the elastic ends half an inch down from the top corners, and have them sandwiched inside of the two black pieces, place the batting on top and pin in place. You can't see where I put the elastic ends in the photo, but they were placed just behind each front pin in the photo (closer to the bottom of the eye patch). Again, make sure that your elastic is away from the edges.
Sew around the edges, starting at the top right side, and work your way round to the top left side. Leave a gap large enough to turn the patch right side out.
Turn right side out, and top stitch around the entire eye patch, closing the gap at the top in the process.