Thanks for your comments and interest! I made another pair for myself, so here is the step-by-step.
Materials and pattern: I just used cheapo craft felt; it's good because it's relatively stiff and stands up on its own. You can make the ears any size you want really, but make a paper pattern so each ear is the same. My large triangle measures 7.75 cm at the base and is 6 cm tall. Cut the smaller one with whatever allowance you want to show on the inner ear. I made sure to mark which side was "up" on my pattern pieces because they weren't symmetrical.
Sew the pieces together! You may be able to glue them instead, depending on what your felt is like. I liked the way the stitches looked. If you are sewing, it is important to have thread that is the same color as your outer ear.
I'm not sure the name of these clips, but I'm sure most of you are familiar with the style. I would have used the matte black ones, but this is all I had to work with and it looks fine.
I krazy glued the felt around the flat part of the clip.
It's easier to take the curves a little at a time.
I don't trust the glue to do the job on it's own, so I tied the felt down as I went with a double strand of thread.
Three inches at the base was just enough to go around the clip into the shape I wanted, with a little extra bit at the pointy end of the clip.*
I tied it down in a total of six places, finishing the knots with a drop of glue to make sure they wouldn't slip out.
Voila! Your fab new ears.
*That's right, I used inches and centimeters in the same post. WHAT NOW.