Or maybe some heavyweight Grosgrain silk? (Black might be a bit "Victorian undertaker" but I bet it would amazing on a Speedy.)
Sort of a cheaper version of this:
https://www.rsmwatchstrap.com/reversible-silk-strap/
As for other, similar, buckles there's these (but NB only in 22mm)
https://elliotbrownwatches.com/blogs...rap-reinvented
And of course there was the earlofsodbury's suggestion:
(Post #4 here: https://forum.tz-uk.com/showthread.p...od-NATO-system)