These are current production and i´d say a tang buckle matching the case colour might do very well!
The deployant clasps are not inexpensive and work best with a slightly padded and somewhat thicker strap, so it might be a problem to find a matching strap for the vintage case. But i find them very comfortable and they make quite a difference on the wrist, so these may be something to consider as well.
If i recall correctly there have been considerations at GP to offer a tang buckle with a 60´s/70´s style particularly for owners of vintage watches:
As far as i know, it´s not an option so far. Doing these would require a certain interest in order to allow for a somewhat reasonable production volume; like with watches, small scales production tends to end up in likewise expensive pieces.
So best to do is to check back with your GP dealer!
Greetings from germany,