The manseibashi tonkatsu sandwiches are still available, although if you really want them, there’s a more convenient place than walking south towards Manseibashi (most Akiba visitors head north towards Ueno and not south towards Kanda).
They are sold inside the JR East Akihabara station on platform 6 (the Chuo line local platform heading towards Kinshicho/Chiba) at the NewDays Kombini (the one next to the Luck Milk counter).