Hello,
Detail of the model can be found on this website : https://www.breitlingsource.com/watch_d ... r_173.html
There shouldn't be a problem to find a genuine a 18k tang buckle at a Breitling AD or folding clasp.
Depending on the budget, the folding would be way more expensive.
For the strap, it's up to your color preference, but as rose gold, I would go in the brown calf strap (brown novo or gold novo calf) or brown aligator.
Regarding the papers, I don't think you will be able to find them as it's a limited edition. Maybe the COSC certificate can be retrieved.
You should ask a Breitling AD. Mine was able to retrieve the history of an Old Navitimer II from 1998 (for which I had the papers).
But it's becoming more and more difficult as Breitling is going "digital" to get the papers.
I personnally would go to an AD ask for a timegrapher test, maybe a service is required & ask question about strap/buckle and then discuss about history of the watch & papers.
By the way : very nice piece
Regards,