The equivalent Kubota model is a D-1005E according to the attached chart.
Try either a local Kubota dealer or an industrial diesel repair shop. When my injector pump failed a few years back, our local shop rebuilt it for about 1/3 of what the Universal distributor wanted. He even had the parts in stock.
I didn't need injectors, but the pump was easy to remove and replace. For injectors, get the right gaskets and torque specs and it should be straightforward.