I'll be staying in Tokyo in early April for two weeks.

The original deal was to stay in Yoyogi 3 in an old 2 storey house (now a rarity in this area) and use the local Sento as the bathroom had seen better times.

Alas, this won't be quite so straightforward as I'd originally supposed.
As suspected, the bathroom actually is knackered. And as old traditional houses in Yoyogi 3 are such a rarity now, the local Sento is closed.

However, there's been a big change of circumstance recently and this is why I'm asking for assistance here.

I'll be taking a passenger with me. The accepted advice is that expectant mothers should not be using a conventional Sento/Onsen.

I know there are Sento with cooler baths in Tokyo, what I don't know how to do is locate them. Anyone have any idea what the options for public bathing are for pregnant women?

Any leads accepted with gratitude.

EDIT: RESOLUTION IN POSTS 21 & 23