Don't think there's many choices for the Miroku 1873.
Marble's makes one and I've read
MVA makes one that'll fit but it's not clear on their website. You could leave the buckhorn but it will cause visual interference. I did that with my original High Wall but I had to remove the elevator in order to get a decent view of the front blade. A good alternative would be to replace the buckhorn with a folding model like the
Marble's #95 to give you better use of the tang peep. I have an original Winchester 1894 that is set up that way, albeit with original vintage sights.