Harness webbing from Tecline. This nylon webbing is 50mm wide and 2.2mm thick. Comes in a 'standard' stiffness that is suitable for a weight belt and still plyable enough for a simple DIR harness.
Note that the webbing does not have a hole for the single tank adapter bolt, (as used on many single tank systems).
Webbing is available by the metre. Weight belts typically require 1.5 - 2m of webbing. A simple harness typically needs 3.5m webbing.
Select the length in metres as a quantity in your shopping basket.