This is one of our shafts. The joint you need is a Spicer part number 5-213X for that end. The two joints in the double cardan are Spicer part number 5-153X.
Here's some info on replacing the joint at home
https://4xshaft.com/blogs/general-tech-info-articles/diy-u-joint-replacement. It's important to note that this shaft is incredibly rusty, so I'm confident that there are going to be some other parts that need replacement. If you watch the video on the page linked above you'll hear me say something about "if the shaft looks like it came off an old shipwreck, it's probably not worth salvaging". This might be one of those. Or maybe the rust is more superficial than it looks and maybe the bearing cap bores and the moving parts of the shaft are not as bad as they looks.