The Moscow Journal of Math says they publish "research-expository articles."

"An important specific trait of the journal is that it especially encourages research-expository papers, which must contain new important results and include detailed introductions, placing the achievements in the context of other studies and explaining the motivation behind the research. The aim is to make the articles — at least the formulation of the main results and their significance — understandable to a wide mathematical audience rather than to a narrow class of specialists."

I'm not sure exactly how that plays out in practice, I haven't submitted any articles there. But it looks like it's worth a try for certain sorts of articles with significant expository content.