When is your trip? Is your priority, the trip or having the perfect car?
The problem here (as you already know) is you might be running out of time.
If I was you, I'd get the major mechanical stuff done first - ie the axle - if theres no new axle casing available visit a few local body shops / welders and see if they can fix it - a new axle case might be what you want in a perfect world, but a repair might do you for a few years and keep your trip on track.
While theyre sorting the axle you can see what overland kit is available via all the above places and work out who can do it or what you can do yourself worst case to keep your trip on track.
You can always throw a battery box and fridge in the boot yourself and get on the road, but if you have no axle you're not going anywhere.