The Hitch and Timber Etsy store sells a variety of small, handmade leather goods, including a series of "notebook caddy" wallets. They come in five colors, all of which will only look better with age:

• Original ($76)
• English Tan ($86)
• Chestnut (pictured above, $86)
• Black ($86)
• Natural Brown ($86)

Each one can hold a small memo book (such as Field Notes), a small pocket knife, a pen or pencil, and some cards or cash. Here's a backside view of the English Tan model:

Every caddy comes with one of Hitch and Timber's own notebooks. Go check 'em all out and pick your favorite. (Note: Some of the caddies on that page are "travel" versions designed with passports in mind rather than memo books.)