You may have to buy the finished product and crack open the casing.
Or get a smaller drive and put your own around it. These things are mass produced in some country so while you could go there and find a maker to do this for you, the costs involved mean you will likely not travel to that country.
http://www.amazon.com/Verbatim-Flash-Drive-96816-Purple/dp/B001UHTDS2/ref=dp_cp_ob_e_title_1 is one of many available that are tiny.
I am trying to buy about 200 2-4 GB usb drives without cases (just the inside part). I am an artist, and will be creating cases for each of them. I have no idea where to start on this one, any help would be greatly appreciated. Thanks!