Kubota's part diagram only lists the boot kit. Unfortunately, I think you'll have to replace the entire shaft. An important service point on any Kubota RTV 1100-series is to pull back both ends of the propeller shaft, replace the o-rings and grease the splines. Kubota doesn't grease them at the factory, and if left alone, the shaft splines get worn to a point (as I'm sure you're experiencing), and the shaft rattles ferociously.