G'day Niko and congratulations.
Crackers asked a similar question on the Beginners Start Here sub-forum, How do I carry a dob, although his question, I think, related to moving it about as opposed to transporting it, which I think is what you are asking?
My answer there was that I used the original box and foam inserts that came with it, but that isn't an option for you as I read your post.
As I'm aware that my original box isn't going to last forever, I'm going to have a wooden box made up for it by a mate of mine who just happens to be a cabinet maker. My thinking is that a well made wooden box will be almost as strong as a metal one, but much cheaper and lighter.
I suppose that isn't much immediate help to you, but it might be food for thought in the near future.
Barring that, all I can suggest is a thick foam mattress and a few old blankets.
Sorry I couldn't be more help to you. Maybe someone else that has been in a similar predicament as you will have come up with a nifty idea.
Cheers mate.