Before I spent that much on a transducer on that old a unit I would post on here and see if anyone has one. I gave a HB unit to a guy needing one and then I got a bracket from a member that had a spare. All my leftover stuff is HB or I could send you a transducer.
Put a post on the main forum or on this one and see if anyone has one they are not using. There are a number of models that will work on your unit so you might want to do some checking to see what will work. Hate to see you drop the money on a new one and find out the DF is not working.
Good luck.