The series went on hiatus with #144 three years ago so Stan Sakai could work on 47 Ronin. Now that he's done with it, and with the Senso limited series, Usagi Yojimbo has resumed right where it left off. #145 was the first issue since the beginning of 2012.
I can tell you from personal experience as someone trying to complete this run, finding the later issues is like pulling teeth. I've gotten up through #121, but I'm missing about half the issues from #122-144. Needless to say, it's really aggravating, as I'm now buying new issues and just stacking them in the corner until I can somehow get the previous issues and finally catch up with the story.
PM sent