I'm fairly sure that Kubota no longer offers any rear remotes for your model. None of the 3rd party suppliers have the valves all nice and tucked away like the factory sets usually are. The valves are going to be exposed, typically above the fender.
So you can purchase from a 3rd party such as Land Pride or Summit for 2 examples. I don't recommend either, but a lot of people buy from them.
Or build a set on your own which is going to be the least costly without any doubt. Be sure that you get valves that do not have excessive internal leakage. Ask whoever you purchase from what their warranty is regarding this issue, it is fairly common with economy-type valves. Most simply don't cover the issue, just the way it is seems to be the common answer from what I have seen.
If you want you can purchase from Fit Rite Hydraulics something similar to what is pictured, but this is not cheap and has a 22 week lead time.
There is nothing like having hydraulic adjustments at your fingertips.
Good luck with your research and decision.