You might get more responses to something like this if you post it in the CUSTOMIZATION thread of the main forum instead of the Kubota area.
However, that said, you should be able to tap the alternator stub on the left side of your engine for the power, then run the wire into a switch that you install on the plastic cowling under the steering wheel. I did that to power a 12volt outlet on a B2910 last year, the install was very clean and it did not require tapping into to the fuse box, which can sometimes be a pain to access.
Check your current draw to make sure your alternator is large enough to handle the extra load, you may find that you are forced to turn some other lights off in order to run the light bar if the alternator is not up to the task. Or, if you are only running the light bar for fairly short durations, then you will probably not notice much problems, the battery may drain down a little bit each time you use it, but as long as the drain down doesn't get too far, the alternator will bring the battery back up. It may shorten the life of the battery under some conditions.