I got one of these when I was living in Finland about 20 years ago, still going strong.
A lot of people asking where they can get one, I don't know, so I decided to make some for my nieces and nephews this Christmas.
In my search for a pattern, found this thread here, however it doesn't have all the answers I need.
I researched further, found this in Popular Science magazine (Thanks Google), extracted and attached here for convenience, and I lost the original link.
After puzzling through it, I made an octagonal one, however mine is 10 sided, and I think much prettier.
I found an online pattern on Etsy for 10 pounds or something, but didn't want to pay, so using free software (Thanks, Inkscape) created a decagon based template.
And then I decided I'd sell my template for 10 euros. wait, no, I attached it here. Hope it helps.
NOTE: Can also scale the base decagon to encompass a CD and use it as a fancy paper/thin card/whatever cd cover if you like (hmm leather CD cover seems kind of cool too)
Unfortunately, I've only found leather in scrap bags at Lincraft, so I've only made a small one in leather to test my template, yet it worked.
If the Christmas presents go down well, I might mail order some better leather and embossing tools so I can up my game, assuming Tandy leather will be best for that.
p.s. The png template is fine black lines on a transparent background. Some image viewers have issues with these sorts of PNGs and just display a black square. If that happens, try a different viewer (any web browser should view and print the image right - though harder to manage scaling)