Sake shops in Kansai Region
I'm a big fan of Shimada Shoten in Kita-Horie; they have a sake tasting cave in the basement where you can try different kinds of sake. http://www.bento.com/kansai/rev/8237....
But I would imagine you'd find Juyondai at many department stores like Daimaru, Hanshin, Sogo, etc.
I'm not sure if these kiosks sell alcohol, but if you go through the underground shopping arcade between Hanshin Dept. Store and Hankyu Dept. Store (in Umeda/Nishi-Umeda), there are kiosks that specialize in prefectural specialties (each prefecture has a kiosk). Maybe the Yamagata one carries it?
(Haven't been in more than a year, so I don't even know of those kiosks still exist. If you're in the area, it's still worth a try!)
I always make a stop at Takimoto to check out what they have in their fridges. It's just west of Pontocho-dori (on Rokujo-dori) - so is very handy for pre-dinner shopping.
Alternatively, pop into Tsunoki if you are heading to Nishiki market.
Jem put me onto Jizake Bar Zen - a great place for an after dinner tasting.