Here's a place you might look at http://www.lucasindustrial.com/products/chain/roller_chain/double_strand/
A picture being worth a thousand words, I went out and took one. The coupling chain is made from the standard parts of #50-2 chain but the center plates are not used and the pins are shorter. This has to be out there somewhere but I do not have a clue where.![]()
As Carl said, that is an obsolete coupling chain. Might start by contacting a Link Belt rep. or someone that handles obsolete inventory (didn't have much luck with a brief google search)
Did you try contacting Carl Sharp.....he seems to have disappeared also. Haven't seen a post in a long time.