3
You could use the
dummy module, rename it to I don't know, say "special" and place your pages in it's folder, still, the only link that will show up in Sitemap will be "Special" it won't have sub links as such. It will show up in your main menu etc. it acts just like a module as such.
If you look at the "Bookshop" link in this
sitemap you will see it's actually just a html page with Amazon Books widgets and code.
Note: I haven't used it with multiple html pages, I have only needed the one index page within dummy, though I don't see why you couldn't add a few html pages that all link to each other from the dummy index page.
That's the only thing I can think of ;o)