Thanks, Jen, for your detective work. Jags, the Adirondacks are an eroded massif in Northern NY state, a spur of the granite of the Canadian Shield just a few hours' drive south of where we live in Ottawa (and just north of Jim K's spot in the Catskills). Lovely area--I used to go hiking there quite a lot, and used to accompany our son's hockey team when they'd go to Lake Placid every now & then to win a tournament.
I believe Axiom is a US brand. The bag is well made, light, and fits to your bike by three loops, two over the bars with plastic friction buckles, and a velcro wrap-around your steering-head tube at the lower back of the bag. Nice wee shoulder strap to carry it, too, à la man-purse.
I have seen squarish variants of this, but not at a store -- only on rental bikes in NYC.
Axiom make a reasonable line of panniers--I use them on my city bike for schlepping groceries. Best feature is their price, about 25-30% of what you'd pay for Arkels.
Cheers,
J.