You could get a small piece of sheet brass (hobby store or on-line) and drill a hole in it to accommodate your existing brass tube. Take this to a jeweler and have them hard solder it at the proper angle and you have your piece. (Sheet brass is easily cut with a hack saw, Dremel tool, etc.)
Regarding attaching it to your bellows: you could drill four holes at each corner and fix it with screws. If you don’t want to make more holes in your paddle, you could fix it with the four screws already holding your leather hinge and pad (but getting these lined up might be a challenge.
Have you considered getting a longer hose (if needed) and re-wrapping the end to simply plug into the hole on the bellows paddle? That is the way my Williams set was made and I prefer it to others i’ve seen. Fitting two tapers is better, but his was made with a normal parallel sided hole and it works fine…wrap with waxed Nyltex or similar.
The bellows in your photo look a lot like the Williams bellows. I was lead to believe that he sub-contracted his bellows out, perhaps they are the same?
Use plumbers silicon, use a grub screw, drill pilot hole on angle,countersink screw, patch and polish
10min done. Only consideration is the size of screw.
Got my Lawrence Thomson bellows back today from David Lim who repaired my bellows by attaching brass plate to the existing brass tube and then screw it onto bellows.