Strap styles and materials are very subjective so you should take a look around.
Hodinkee straps can be nice, but they're quite expensive and can't be customized.
Bulang & Sons re-sell JPM straps and they're probably nicer than many Hodinkee offerings for a lot less money.
Veblenist straps are of similar quality but can be customized easily.
Wristwatch.me straps are custom-made so will take a bit longer to arrive, but are very nicely matched to vintage watches.
My personal recommendation is, if you're not sure about a color combination, try getting a few cheapos from CheapestNatoStraps (who are currently running a 70% discount on most straps) and see how they work; then spend some money on a custom strap.