Yesterday, I went to get my travel sewing machine kit with little tools to remove a throat plate and the odd bobbins I keep for testing machines were a tangled mess. Years ago I saw a tip for making an inexpensive bobbin tray from 5/8" OD - 1/2" ID vinyl tubing. The tubing was purchased and sitting in my workbench drawer waiting. I finally made the tray and it works great! It holds the bobbins tidily in the pencil case I use to hold the tools.
Use sharp and strong craft scissors to cut the tubing to the length preferred and then make a lengthwise cut to separate it. The heavy tubing has enough strength and memory to hold bobbins of slightly different diameters securely. Additionally, the tubing can be cut to make small collars for each bobbin but I find them more difficult to cut for the narrow Class L bobbins for my two Pfaffs and they are difficult to remove on larger Class M bobbins that have only a small amount of thread on them.