Cracked it! Well I think so... Solution (well for me or for anyone to wants to create something like a plastic carrier bag) was to create a rectangle with rounded corners and a rounded top.

Load into meshmixer and use the sculpt option until it resembles something like the real thing. You might need to make 2 separate parts and join together in your modeller.

Either way you'll get a very large mesh, around 12mb. So fire up meshlab, and play around with the decimation options until happy. Then it's some jiggling around in the modeller/mapper etc with smoothing/triangulation/remove co-planer etc.

Next was to add some thickness to just the lower section to give it an edge.
Followed by adding the clear vision screen & screen frame, so that part will be flat and level.

You could also model & map the vison screen and frame as separate materials. Say to give the screen a different colour from the main hood.

For the plastic effect, you could use an app native glass material, use that shader mentioned above, or (as the image) simply tinker with the transparency settings.

To to fit it just dial it into place, you might (ok will) get pokethrough. For body pokethrough, tinkering with the axis dials will reduce that. For hair, it depends on hair length.

Also don't forget to adjust the scale dial, depending on whatever figure you use. BTW - this one will be packaged up and put up for free over the weekend.

Pinky - you left the lens cap of your mind on again.