A good number of years ago, I was in a similar situation. In my case, I had forgotten to buy something and was meeting someone the night of my arrival in Tokyo. I just picked up something at the Duty-Free before departure. I was flying NH HNL-NRT in Biz (they had no F on the plane), and I asked the FA if she knew when the Tsutsumu Store in Shibuya closed (I was hoping that it was something that other passengers may have asked about in the past). She had heard of it, but didn't know the closing time. A few minutes later, she came back and asked me if I was fine with her wrapping it with some tissue paper she found on board. I was very happy, and thankful to her for her gesture. Needless to say, the wrapping job was beautiful (even though the paper had ANA written all over it). I doubt they would do that these days, but if your flying F on JAL or ANA, it wouldn't hurt to ask.

On a side note, I have used Tsutsumu in Shibuya in the past, and they do very good work.