You might be better off looking for thin packaging tubes or similar.  Any composite tube of that sort of diameter is likely to have a wall thickness around 1 - 1.5mm in typical applications.  

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

I am looking for something like a plastic tube approx 30mm OD and 1 meter length. It needs to hold its shape but does not have any structural requirement, it is strictly cosmetic. It needs to be very light, so a really thin wall, less than 1mm.

Even better would be an egg profile or oval with flattened sides.

If no such tube is available, then some  kind of plastic sheet that I could gently drape-form and would then retain its shape .