For What It's Worth:
I too had to replace my Kubota top link because the threads went bad. I purchased a short top link from a 3rd party that looked just like the one pictured.
Some potential problems:
(1) In my case, the Kubota's top link used "fine" threads while the 3rd party top link used "course" threads such that they would not be interchangable. As a side note, now that I have used both, I really like the course thread design much better.
(2) The top link end on the 3rd party top link was too wide to fit into the Kubota top link holder bracket. This problem was quickly fixed with a grinder.
(3) Once the grinding was complete, the 3rd party top link worked just fine on my B2150. However, there were problems using it on my B7100 because the rod that is used to help adjust the top link length would jam right into the ROPS when the 3-point lift was raised. On the Kubota top link, the "assist mechanism" (or whatever you call it) was off-set from the middle of the top link such that it didn't cause a conflict.
(4) The LENGTH of the 3rd party top link was adequate for both my B2150 and B7100. However, my experience has shown that top-links for Kubota BXs need to be shorter than the one for my B7100.
Hope this helps,
Kelvin