Call me crazy, but I try to make all my own mailers. I follow this tutorial and they turn out pretty well, as well as free and gentle on our planet.
I start out with a whole big bunch of plastic bags (which always seem to multiply pretty quickly, despite always having at least 10 reusable bags in the trunk of our car at all times).
Setting up with two big pieces of craft paper, my iron, and something underneath to protect the floor…
Take heed, if you stop mid-ironing to take a photo of said ironing, you will burn a whole in the middle of your plastic. D’oh.
…that big bunch soon turns into a little stack of smoothed plastic fabric.
Sandwich those babies between some reversed brown paper grocery bags, stitch up the sides and – yay! – a free, recycled, handmade mailer.
If you devote an evening to making a bunch of these at once, you will get a bunch done and be set for awhile. No way would I make these as needed!
I get lots of great feedback from customers and the ladies at the post office for these, and I feel they add a nice little handmade touch to all orders I ship out.