The spoke lengths for all DT Swiss System Wheels according to the model year could be found here Workbooks / Techbooks
Spoke lengths for custom-built-wheels with Classic Hubs for J-bend spokes could be calculated here Whizz-Wheels Speichenrechner
For straight-pull hubs spoke lengths could be calculated here DT Swiss Spokes Calculator
If you already know the needed spoke length, you could search easily by typing three digits XXX (for example 272) in the Shop Search -> as a result all available spoke types in this length were displayed and could be chosen.