You can get the Corflute from Bunnings. They have two thicknesses - for you SCT I'd suggest the thicker one.
EDIT:
There is another option too. Rather than Corflute, you could get your hands on a car windscreen shield, really cheap from $2 shops. These are reflective on both sides, and will offer more insulation for your thin walled SCT. You can cut it to size, and also place that black felt on it.
Below are a few pics of how I prepared the Corflute for my Mak. It rolls up nice and tight and holds its shape nicely. I also cut some slots and holes to accommodate the various bits.
Thanks for the compliments on my sketches too,
Alex.