Make page permalinks end in .html

We’re migrating about 2000 HTML pages to WP…by hand…

I see no solution in the fora to the question of how to get WP’s Page (not Post) permalinks ending in .html – we want the old physcial pages to retain their URL when they go into WP

I know this has no bearing on SEO whether an URL ends in / or .html – it’s simply so I don’t have to get a very big set of permanent redirects going on in .htaccess.

Solution or hack, please?