I’m looking at delugs too and I believe they’ll make them in any of their materials via a custom order: https://delugs.com/products/custom-watch-strap-cartier-santos-dumontTheir service and quality of their leather goods are immaculate. Not comparable to a camille fournet of course but you‘re only paying a fraction let alone not even cartier such standards.
Their inserts look well made for the dumont line. I wish their range of materials for the dumont straps would be a bit larger.