In a blast-from-the-past, I use one of these:
Which I purchased from here:
Office & Desk : Flarose - Ansett Australia Merchandise
(last item on the page).
It's Oroton leather, that was originally given to J PAX on the 744 AN services. The one I bought came wrapped in AN Wrapping Paper, and had a little card stuck on it thanking me for choosing to fly AN J.
It's actually a really good travel wallet. It's a very solid zip, the 'leash' it has is just clip-on so it's easily removable, and inside it has a small zip-pouch which easily holds most foreign currencies.
I use it to hold my collection of Express inwards/outbound cards (getting quite the collection now!) as well as my backup/supplemental credit cards (in case I lose the ones in my wallet whilst travelling) and my other "frequent xx_xx_'er" cards.
$25 for an Oroton Leather travel wallet is a bargain IMHO. The AN embossed logo just makes it plane-geek-retro-cool