In 2020, I found an upload of a Japanese documentary from 2000 about the Kankoh-maru single-stage rocket proposal, which also used clips from the anime (timestamp 5:13). youtu.be/8J1Id_eJue8?feature=shared&t=313
In the past week, someone tweeted to me about the documentary Rocketships (1998), hosted by Kate Mulgrew (who starred in Star Trek: Voyager). There was a segment talking about the Shimizu space hotel at timestamp 28:39. youtu.be/ENpwB7CMLzc?feature=shared&t=1719
Looking it up, the full film (10 minutes and 45 seconds) is apparently hosted in the Swiss Museum of Transport of all places (the page is broken as I am posting this, but it wasn't an hour ago)