ooooo, are you going to make your own ocarina? Thats exciting!
First thing though, do you plan to make one that is able to play notes. Specifially, on-tune notes. Because that could be tricky.
If it's purely for visual wows, go for it! That way you could make it to fit your hand too!
If you are seeking a playable LoZ one, try buying one online. I have the fairy ocarina from Songbird and its beautiful. Both to play and look at.
On topic though, Eckersleys may have something. They have an online store to make it super easy.
I also found these guys:
It looks like they ship around Australia. Give them a go.