Did you try eBay or Kijiji? Think I saw one on there awhile back.
I recall my buddy in northern Ontario having the only Hindle back in the mid '80s Sounded like NOTHING ELSE, rivalling the Kerker Comp baffle in decibels for certain, maybe even louder.
I believe that it is a true 4 into 1 as well. Not like the current Hindle I have which is 4-2-1.
A new Hindle still tunes up nicely with a Dynojet Stage 7 I might add.
I have 2, a 14" Super Sport and 18" Stealth Carbon Fibre baffle unit. Ride the 18" much of the time for the looks of it on my '06. But for audible sound I run the 14".
Good luck in finding the proverbial needle in a haystack.