The old-school version was the subject of a search that took me to most every Polish bakery on the southwest side; you even responded to the post!
http://www.lthforum.com/bb/viewtopic.php?f=14&t=8982Definitely try to hit up Europa. I found after a trip there that they sold it at a grocery much closer to me, Family Pride, on 107th and Pulaski. Might want to call and ask if they sell it to any other purveyors.
As for Japanese cheesecake, I can't help you out. But finding the esteemed SW-side spongy cheesecake definitely brightened my life by a notch or two. I think you owe yourself a visit.