I have a few USB thumb drives that are for installing the operating systems and for storing files. I have been getting them mixed up and wanted to note what was on them. I do have small envelopes that are used to store trading cards in but thought they might generate static electricity and may not be good to use with the thumb drives.
I did remember in the early hours one morning seeing small paper envelopes somewhere around where I live. It took me a while to find them but they come under the name of seed or pay envelopes.
The only size available was the Tudor No. 5 Seed Pocket Envelopes 50 Pack. It fits the thumb drives I have here. Went over to the section where the shop sold the thumb drives and checked various ones and it looks like they will fit most size of drives they had on display.
You get fifty and the price was reasonable. You can label them or just write on the front of the envelope.
Hope this is helpful.