Ooops totally forgot the internal divider :wacko:
For a strap, you can use an old seatbelt (free from scrapyard, or take one out of your parents car, they wont mind). Once you cut it to the correct length, melt the end of the strap with a lighter to tidy it up and stop it fraying.
Feel free to knock one up using cad software, I would do it, but I haven't learnt cad yet, just photoshop.
The design above, was done with mspaint for ease