You can get a parts catalog and a ops manual from the Museum. I have both for my model 207. The yoke part # is 5312100 for the model 207 - not sure if they are the same though - no dimensions listed. I could measure mine if needed. Is your u-joint completely missing? Our home town ag/auto parts store could probably match one up if i needed one and if not I would call Jerry Stairs or Brad Maibach and they could prob get one. 

The jack mechanism is showed good in the manuals. They were not that good when new. I have the same thing on a 62W baler. I noticed on the 720 baler they went with a bulldog type trailer jack with side crank. I love staying original but both on my 207 and 62W the jacks are toast and i will be going with the side crank swivels.