I think the author who did the Leomon one shot said on twitter they weren't interested in posting theirs's but its been a while. It would be a shame if the last two never saw the light of day.
It's so weird this site used to have all the chapters but after a major update that was more than half a year ago, half of them got deleted. The same happened for other arcs of higurashi. It's so weird. I wish there was a way to get them back...