You may have noticed the name of our editorial director Damien McFerran has been largely missing for the last couple of weeks, and that's because he's swanning about on Holiday. He still has time to browse random Japanese accessories online, of course, because that's just his style.
In any case, he sent us poor worker drones a link to the following 'Super Switch' accessories on Amazon Japan, notably the following Super Famicom Joy-Con kit on Amazon Japan. It's a thing of beauty, assuming it doesn't have materials that do anything horrible to the Joy-Con controllers; it seems to be relatively safe, with a review average of 4 stars from those that have bought it already.
This product page has all sorts of designs from the same company, including some bright colours for the back of the Switch tablet; they're all rather nice, but the Super Famicom Joy-Cons are our favourites. We searched on Amazon UK for the same thing but ended up at a page for some sort of cleaning product, which was underwhelming to put it mildly.
And yes, we'll probably try to import some of these and let you know if they're any good.