We can't recycle any foam in our area, so I've saved the packaging (not styrofoam) from large ticket items like the microwave and TV so I use them to stick my needles into and can glue a piece of cardboard or cardstock for the key.
That's great. I'm in oz too and have the same problem with craft supplies. Cheap to buy on the net but the postage makes it uneconomical . Do u have the specs for your organizer? I'd love to try to make one.