Mailer
Quill Brand Packing List Envelope, 6 x 9 Resealable, Clear Face, 1000/Case (RCF69) (6 x 9)
Amazon
Clear Adhesive Side Loading Packing List Document Envelopes, 6" x 9" Resealable Pouch for Attaching Packing Slips, Invoices and Important Papers to Packages, Shipments and Mailings (Pack of 1000)