Yeah, the chain used in bottle cleaners is the stuff I was talking about (attachment chain). The use of attachment chain for tracked drive is very popular among RC tank hobbyists. I did a bit of investigation, and it seems that the sources of surplus attachment chain has dried up in the United States.

I found out that a major manufacturer of attachment chain (Renold), does offer retail sales. Coincidentally, this is where the Mortis team got the material for their tracks. I will give customer service a call tomorrow to see how much several feet of the stuff would cost.