The Brown Olive is certainly a nice choice for the 68.
The Black Crocodile is a must for the 65, with the black Calf, or a Leather Nato.
A tropic would be very nice and historically à propos , and as µI speak of that, I found in Paris a guy who sells them.
Re to the Amvox II DBS or Amvox III Straps, yes, they are superb, but, IMO, a bit too " technical " for the Polaris.
Too modern, if you see what I mean.
As for straps in general, I must say that in Paris, we are very lucky to have a wiede choice of strapmakers.
They all have their good and bad points, but the good thing is that you choose the best from each of them.
Best,
Nicolas