Jandd Mountaineering still makes these, it's their Gabriel Messenger Bag, which retails for just $130. I'm pretty sure they're still making them in California.
Besides utter durability, this bag has some great features that set it apart. First, it has a waist belt which distributes weight to your hips instead of shoulders. So, for example, when I picked up a new laptop today across town in St. Louis Park, I hardly noticed I was carrying it the whole ride home.
I also like its water repellent Condura fabric, which has always kept my stuff dry but doesn't shed the reflective tape I attached a few years ago. More modern weatherproof fabrics seems to just sluff tape off.
Finally, I like its gusseted zipper, which pretty much doubles the size of the bag and makes it twice as versatile.
Perhaps one could fault Jandd's somewhat 90s styling or their charmingly retrograde website, which has zero hipster points. But there's plenty of bike accessories out there with flashy marketing. If you want a bag that works great and lasts forever, get a Jandd. Or, better yet, ask someone else to buy one for you as a present.