Well, after some roaming about the dollar store looking for duct tape, I found pool noodles, made of foam. Since my kid is small, I decided I could use these noodles for her arms.
So I bought one for $3. I cut it to length, then up the middle so I could get it on her arm. Then I drew the raised cyberarm design - freehand so it isn't perfect and cut out the middles. This is the blue foam.
Underneath I glued the craft foam (orange foam) under the blue foam. I glued the dowel rod to two foam pieces that I glued in the raised portions as well. I created the "bolts" via a quarter and a dime I cut out of foam.
I have plasti-dipped them, but no pics yet.
It's not perfect, but I suppose it will do.