In a bind you can use paper that you use for your printer. You have to trim it down . It works great. It will tell you not to cover the bar code but I cover it all of the time with clear tape and my packages get to the destinations just fine.

A few postal workers have told me they prefer clear tape over the bar code if printer paper is used. When it is raining or snowing it will protect the information.

If you use Paypal there is an 18 cent delivery confirmation fee. It is well worth it.