I bought these and love them. https://www.amazon.com/Adhesive-Loading-Packing-Shipping-Envelopes/dp/B01IP1G0W2/ref=mp_s_a_1_3?dchild=1&keywords=shipping+label+sleeves&qid=1587097204&sprefix=shipping+label+sl&sr=8-3

I have some customs labels but I still had to tape them shut.