I have a friend that works in an opticians and when they order glasses they arrive in bubble wrap pockets about letter size and because they don't reuse them she brings them home to me, they are great. If you have a letter size portrait to deliver just cut one or 2 up the side and slip the portrait in. Also great for small items just cut to the size that you require. So pop into your local optician and see if they have any that they can give you they really are useful.
Marg