DeviantArt user batman-n-bananas made a very fetching steampunk Portal gun. But what to wear with such a contraption? Why, mechano-Victorian long fall boots, of course, in which fancy modern tech is swapped out for reliable British steel.
These are wonderful. And while they fit the "Steampunk Portal" brief perfectly, I like to think they'd be just as suitable for a future in which Mary Poppins wanders a post-apocalyptic wasteland, killing mutants with her salvaged umbrella swords.