Target has wine in 375 ml single-serve cartons similar to juice boxes. My local grocery store has "Bandit" brand wine in 500 ml cartons, and I think they have smaller ones also in a different brand. I've only had the Bandit Sangria, which I thought was pretty decent, but I'm no wine expert. I haven't taken it backpacking but I had it at a campground along a river where glass was banned.
It never got mentioned, but the entity making The Climber Pouch is Clif Family Winery, of Clif Bar fame:
This is their old wine label, and you can see the similarities with their energy bars. (The new labels not so much so.)
That style of pouch is the most innovative packaging I've ever seen for wine to imbibe in the outdoors, but it seems like it would go better carried in some bike panniers than in a backpack -- and Gary Erickson, co-owner/founder of Clif Bar, originally came up with his energy bars from his cycling. His cycling is also how the Climber wine pouch came into being.
And it's very green, too, and it sounds like it is decent wine and a step above box-o-wine. A great idea for an outdoor excursion other than backpacking.
They are available in pretty much any grocery store wine section that I've seen around here in NC, and I know they are also available in AK. I haven't looked anywhere else. They are a little spendy compared to a standard bottle, but there are some decent (or at least drinkable) brands out there. Next time I go to the store I'll take a photo.
YMMV. Viewer discretion is advised.