I've featured a couple of bags before in a similar style, but I wasn't entirely sure about them. I think this Paul Smith version is the best I've seen, though.
Leather with, obviously, an airmail print, it costs $200 from My-Wardrobe.
Related: Yves Saint Laurent's Y-Mail clutch gets it right | YSL's Y-mail tote | Tyvek® wallets from the MoMA Store