Okay, I think I got some decent news for you. Kubota does make a V2403 in a turbo version, output is 61 hp. It can be found in the Bobcat t190 skidsteer.
Actually, a friend of mine owns this model bobcat. As I recall, the bobcat used the MHI TD03 turbo. I was looking at it the other day to see the turbo set up as I am going to be turbocharging a kubota engine in the near future. Anyway, you can go to your local bobcat dealer and take a look at the T190(it is a new model) and check it out. The turbocharger will have a metal plate with id numbers so you can get the right one. Bring a flashlight because the turbo is bolted to the exhaust manifold which is behind the motor so it is dark in there. Good luck.