In case anyone else had as much trouble locating these items as I did, I thought I would post the source I found.
I found them at McMaster-Carr (McMaster.com).
So if you want to try tilting your seat back, this is an easy way to the the rod-couplers.
The item is part number 93020A781. Case-Hardened steel 8M coupling nut. 1.25pitch, 19mm length. The length (3/4") is perfect.
Their phone number is 562-692-5911