Replacement for Unique balance 21C

The spring inside one of our channel balances broke and so I'm looking for a new channel balance to match the one we currently have. I included 5 photos of the current balance. It's 22" not including the plastic ends. The names and numbers on the back bottom of the metal channel are:

"23:08:05 05/18/04 UNIQUE BALANCE 21C"

Hope that helps, let me know which of the channel balances you have for sale will match mine.