Choices nowadays seem to be rubber insulation w/fabric cover (as original), PVC insulated w/fabric cover, and 100% pvc insulated. For the conductors, my choice would be PVC insulated w/fabric cover, unless you're striving for 100% authenticity.
The outer braid choices are fabric (as original) over rubber or pvc insulated w/fabric cover, or pvc (non-adhesive tape) wrap.
The pvc insulated conductors w/fabric cover and the fabric outer braid loom seems to me the best choice of original appearance with modern longevity.
The last couple of harnesses I bought were from brit-boy on Ebay, and those too were likely from Autosparks; all appropriate connectors, etc, and easy to fit and connect__relatively speaking...