Catrike Automatic Chain Tensioner

I have an Automatic chain Tensioner that was on my wife's Catrike Villager. She had short legs, so I paid an additional $150 for this add on to her bike when I bought it new, so that it would be easier to adjust the boom when someone else wanted to ride it. She put about 5 miles on the bike, and my daughter put about another 15 on it, so this thing is practically brand new. Sold her bike last summer and took off of bike before selling it.
Would like to get $100 for it if possible.

Here's what it looks like on a Catrike Villager. Should work on any Catrike