This project re-purposes a typical $2 convenience store sewing kit, minus the unusable scissors and thimble. Cheap-o kits don't come with very good thread so there is also the option to just buy a 98 cent pack of needles and use thread you have laying around or buy some good stuff that coordinates with your wardrobe.
Below is a PDF of the template, some card stock is all you need. Version 2 has side flaps which make it just a little thicker but hold it together better if you're storing it in with other things. Cut all the way to the edge of the page on the labeled end and you'll have a nice flap to tuck in and keep it securely together.
Step 1: Cut Out and Load
Just cut one out and cut out the indents in the center section. Then with the tip of your scissors make a row of notches in one indent, one for each color you will stock, to hold the start and end of the thread.
Load it up with thread, stab a couple needles and a safety pin through, tuck in a needle threader if you want one and you're almost done. If you're going to carry buttons just unwind a little thread, slide them on and rewind, they're captive.
Step 2: Fold and Stow
In the event that you need an even smaller package you can just wrap some thread around a pack of needles, but the cover flaps on this design will help keep thread from tangling and also clean.