Lily, if we are talking about the same things, they are called cable ties, as they started in the telecommunications and IT world (I think) and spread rapidly to all industries where people have so secure cables together or to a support point. They are used a cheap handcuffs in some countries.
They sound like a good idea for locking a case - just need to ensure that you have a good knide, pair of scissors or Leatherman on you to cut it open.
LR: Check your PMs for detail.