Tech Order/NAVAER/Eng Order/Air Publication binders?

[Sabrejet]

Way back when, I had a source of heavy-duty binders for Tech Orders etc, but I've run out and that source has dried up.

Does anyone know a supplier of the heavy-duty type of TO/NAVAER/EO/AP binder? I'm talking about the type that uses straight tube or straight rod binding, not the snap-shut, lever-arm type.

Any help much appreciated!