I wanted to recommend the kosher food delivery service from R Mendi/Channa's Place. Website and order form is here.
https://www.chanasplace.com/onliYou need to order and pay online.
Note that they will deliver same day anywhere in the country for a fixed charge of 3000 Yen, approx US$27. I had business meetings in Takayama, which is around 6 hours drive/train from Tokyo - food was shipped same day via refrigerated delivery service, and arrived by 5pm at my hotel (where they were more than happy to microwave it for me).
I have now had 2 deliveries, and have tasted many of the menu items - all are good, especially schnitzel, turkey skewers, chicken sandwiches. They come very well sealed and packaged. I think costs are reasonable, given that Japan is not cheap anyway and it's very hard to get hold of kosher meat. Ran around 2000 Yen/US$18 for meat meal, around 1000 Yen/$9 for a meat sandwich - bit less for tuna/egg. He also does shabbat packages with wine/challot etc etc
I would recommend without hesitation - it makes travelling all over Japan much more fun without needing to worry about food.
Let me know if any questions.