Yesterday there was a stall in Durham indoor market that was selling some thin elastic cord – exactly what I was looking for to finish my modification to my pack. I had a suitable cord grip and bead in my camping box – the bead is needed so the cord grip does not come off.
Using this thin elastic cord I can still pack the travel bag into it’s miniature stuff sack.
See more details about the modifications here.
Update
The thin elastic did not work, it got tangled up when I was using it to hold my waterproofs onto the bag, so I have replaced it with thicker elastic.