G'day AlanB and welcome!
If it were me, I reckon I would build my own hollow core door (to keep the weight down) to fit the jamb (like a torsion box). Frame, thin ply on the back, ship lap on the front. Then I would get about three "invisible hinges" to hang it with and use some magnetic push-pull catches so I wouldn't need a handle.![]()
To match the grain and colour, why not have the chippies (is that the right word?) lay the ship lap across the door opening just as though it were the wall, mark it and cut it at the door opening and number each piece. Then build the door using the ship lap in that order and the grain and colour should match pretty much exactly. If you get the edges to good tolerance and use concealed hinges, the door will virtually disappear.:eek: