Thanks for the info. If it helps you when you revisit it next year I'll post what solution I come up with.
From my research so far for a full tailgate replacement it seems there are two main options: either OEM or non-OEM from alibaba.com or similar. As with all things Toyota Land Cruiser Australia seems to have the widest and best options. Even with shipping costs for me it'll likely be cheaper to import from there a full door replacement, whether that's OEM or second hand. I've reached out to some local dealerships and 2 European Toyota breakers to see what they can provide.
At the moment I have an on-board compressor so I plan to deflate my spare to fit it underneath the car in the original position.
I'll let you know how any tailgate replacement goes.