Great project - hope to see it soon in PROJECTS. I use the big spools - so this wouldn't work for me.
I have just found what I was looking for. Here is the link. I saw a lady with one this evening and she had a strip of fabric sewn into the seams just below the zipper and she had pulled the thread thru the fabric with a needle and left a little hanging on the outside. Then when she need some of that colour she pust pulled out the lenght she need, cut it and left a tail hanging again. She had put a pocket at the bottom and a some batting in a little book at the top to hold needles. Will have to make one and post a picture. Hope the link works.