I don't know where to get a ready made crate to ship off said driveshaft.
When I had mine done first, from Portland, it was an exchange. I was on the phone with them probably less than 2 minutes for the order process, and you send the core back in the crate it came in. If you are the kind of person who absolutely has to have your original rebuilt instead of an exchange, (or if they don't have what you need in stock) I'm sure either one of those places would send you an empty crate. That's what Metric Motors did many years ago for my engine rebuild.
Anyone living near any kind of major airport has plenty of freight forwarders and thus, craters, nearby who can whip one up for you quickly.