Barry,
Auto spares (eg Autobarn) shops sell sleeving in different diameters. It is quite heavy-duty and used for bundling electrical cables in autos ( - would you believe?) I have used it to bundle my caravan power and electric-brake cables. It is fairly firm and split so that you can cover cable bundles which are already fitted with connectors or have the ends attached.
I assume you do have these type of shops in Canberra.
Robert