What you'll need to make your own:
-Long sleeved shirt
-Needle and thread
-Sewing machine/serger (I used both in this project)
Step 1: Cut off sleeves
I cut mine off as close to the seam as I could because I wanted them to be as long as possible, but you can really make them any length you like.
Step 2: Fit them to your arm
Turn the sleeve inside out and put it on your arm. On mine, I wanted them to hang down to about my knuckles so I fit them with that in consideration.
Using the original seam as a guide, pin the sleeve so it fits snugly on your arm. (It was sort of hard to do this one-handed so you may want to have a friend help with this)
I then serged along where I pinned.