It's unlikely that I will find this special size sprocket so now
I am researching the various ways that I can have it reproduced.
Ultimately, I would like to get 6 of them made (see attached photos).

I am starting to investigate CNC machining, casting or 3D printing.
There are some very good videos at Jay Leno's Garage on YouTube which
explain and demonstrate the latest technology in laser scanning and
3D printing of metal parts:

  https://www.youtube.com/watch?v=bwFspzVGUF4&t=5s
 
  https://www.youtube.com/watch?v=d1DYKMxfn7Y&t=118s
 
  https://www.youtube.com/watch?v=n60NibYbPqQ&t=89s
 

The Stratasys technology looks like it can easily do the job,  but
it's also prohibitively expensive (at least for me).

It seems to me the first step I should take is to have the part laser
scanned.  From that computer file I would have several options for
making the parts.

Shapeways.com, mentioned in Jerry Vitale's MMD post of April 19, looks
promising, but their website leaves a lot to be desired and I will just
have to contact them for detailed information.

Any input from MMDers on how to go about doing this would be greatly
appreciated, since for me technology ended in 1930 -- all of this
modern computer stuff is very perplexing.

Thanks,
Dave Krall

 [ http://www.mmdigest.com/Attachments/18/04/24/180424_053929_100_4242.JPG
 
 [ http://www.mmdigest.com/Attachments/18/04/24/180424_053929_100_4243.JPG
 
 [ http://www.mmdigest.com/Attachments/18/04/24/180424_053929_100_4244.JPG
 
 [ http://www.mmdigest.com/Attachments/18/04/24/180424_053929_100_4245.JPG