Make sure the tractor is off, bucket on ground. Relieve all hydraulic pressure off the bucket by moving the valve controls in all directions a couple times. Get an open end box wrench that securely fits the fitting. Righty tighty -- lefty loosey. Grab a rag to sop up whatever comes out of the hose and cylinder.
Either take it to a hydraulic shop (heavy duty truck shop) or most Kubota dealers will have the equipment on site to make custom hoses.
After you get one made, installing it is the same as it came off. After installing, fully cycle the hydraulics several times, then put the hydraulics under some stress (in your case, you should be able to pick up the front end). Keep it there for about a minute. Then let the tractor down, fully relieve all hydraulic pressure, then check for leaks.
NEVER EVER grab a hydraulic hose while the machine is on or if the hydraulics are under pressure! If you need to check it while it is under pressure, use a piece of cardboard!
If all is good, then you are all set.
Hint/Tip: If it is a weird angle (ie: custom fitting), most likely a simple 45 degree will work. Like say on the loader controls or off a cylinder. Rarely do I run into where I absolutely need a factory specific hose. Another tip, you can always go a bit larger on the hose diameter -- never smaller.