I have a good stack of envelopes of different sizes. some padded some not. All perfectly usable. (See pics).
Some are in very good condition, requiring just a label and some tape. Some others just require some more tape.
I can deliver or post them to you, depending on your location or you can, of course, collect them yourself (location shown on the title).
BEWARE: I always reply. Please, check your spambox.