I don't think I've ever seen that drawing online. Simon Mills' last book, 'Hostage to Fortune', has the drawing in it; it's not a really cheap book; perhaps you can pick it up from the library if they have it.
They're not on our Britannic site -- the first class lounge, anyway. As you know, there are others such as the swimming pool and first class grand stairs. The Flayhart/Shaum book should be available in a good library. I may be able to e-mail an attachment to you if I still have a scan on computer, as my originals have gone to my publisher for setting.