I think Microsoft's Bing Translate matches the features the OP is looking for. Like Google, it's part of “Big Tech,” but at least there's a competitor to the oligopoly.
Aside from Chinese-based services, other well-known translation services that support Japanese include DeepL, TexTra, and Plamo; however, I couldn't find any of them that offer the feature to display Romanized spellings alongside the Japanese text.

https://www.bing.com/translator/
Additionally, an Android application called "Offline Translator," released by DavidVentura, is capable of performing this kind of Romanization while offline.
