You’re a little further away but Wing/Henshaws make great tubes. I’m sure they can send them to you but shipping across the world is a bit more expensive these days. They did many of the original 733 tubes. In the States a new set is about $10-12k US and used ones seem to go for $4-5k US.
I got new tubes from Wing a few years ago but they were special because I have the predecessor to the 733. They were a great company to deal with.
Going from inboard to outboard requires a small addition to the back of your boat. They are almost impossible to find but Zodiac made an aluminum bracket for that, I managed to find one years ago and did that. I think you’d probably be better off making one up out of fiberglass. That also gives you the option of going full width on the hull for a bit more floatation if you are thinking twins. Look for Ryan Pratt’s old threads in here, he did that to several boats. He used willards but they are almost identical. You can also try to contact him, he was super helpful.