Check with an industrial bearing supplier, or a farm supply like Co-Op. Most of those joint assemblies aren't repairable, just replace the whole assembly. I notice the joint you've circled doesn't have much support. The pillow block bearing that supports the shaft should be very close to the u-joint, or the joint will fail very quickly. I maintained a fleet of wreckers with shaft-driven PTO winches, so I've seen that problem frequently!
Jerry
