Here it is:

The first prize was a standard retail train-case, seems crazy, but there we are. I’m not sure I understand the description entirely, but the lottery was over in a week and the odds against winning appear to have been high!
https://www2u.biglobe.ne.jp/~akeda/DOLL/b-orepura12.htm
It looks to me that in each store, the first hundred customers that bought a qualifying item got a lottery ticket. Of those one hundred tickets just one won a train case and three won the E4 Max. If we knew how many participating stores there were…….but we don’t. Yodobashi and Bic Camera are both mentioned, and they both have quite a lot of branches, but even so I think this must be a pretty rare item, and a very good buy on your part. ¥6,500 plus fees etc.