Thanks to Magirus for this interesting and illuminating thread. I have five Havestons and they are excellent quality and offer such a clever solution to the double stacking of the strap under the watch with their single pass idea. There's no longer a need to butcher NATOs anymore.
However, I've not yet tried one of their canvas series but have a hankering to do so, particularly for my PRS-29B. It's currently on the Haveston M-1936-B which goes very well.
https://www.dkpw.co.uk/watch/prs29bh3.jpg
I used to wear it on one of Eddie's canvas straps which were great although far too short! They were short 8 or 9 years ago, and many pies later, they would be impossible now. :(
https://www.dkpw.co.uk/watch/prs29bmap800.jpg
So I think a Haveston M-1944C in OD green may have to be purchased. I'll hold off for a while, as I have a a Vostock Amphibia coming in from the depths of Russia. That will need a Parade series NATO but I'm not sure of the best colour match until it arrives. :)