Help - Bird Crate for international travel

So I’m facing the situation that I might relocate back to Germany and hence want to bring our cockatiel Morty along as well. I’ve got some decent information about the overall documents I’ve to prepare and am now looking at options for a crate.
I will need to do most of the shipping process myself, as where I live (Hong Kong) somehow ppl only ship dogs and cats.

Hence I’m currently looking into buying a small dog crate and modifying it. Does anybody have experience in this or
any tips or even perhaps a better idea?

Any advice is very appreciated as the sheer information of relocating itself is quite overwhelming.