Hi Shaun,
I HAVE NO IDEA  I got mine at no cost from a group called the Country 
Cousins.  I think Handi Hams also have one ore at least used to have one. 
It is possible that you can find a fellow ham to build one for you. 
Basically it is just a audio oscillator.  The same thing that is used as a 
practice oscillator for CW.  You should be able to have one built for $10 or 
$20 and I am not sure how much that is there.  I hope this helps.  73.

Walt
WA4QXT
New London CT
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