People's tastes/requirements vary so I cannot really make recommendations. I can say I've had good experience with NATO's from Haveston , Crown and Buckle, Clockwork Synergy, and NATO Strap Co. I convert all my NATO's to single pass by eliminating the second keeper but Haveston and C&B offer single-pass versions.
Here's one article that may provide some ideas:
The 10 Best NATO Straps for Watches in 2021 - The Modest Man