If you get a SOHC/4 off off ebay you will more then likely pay a very high inflated price. In years past it wasn't to bad, but nowdays for the most part its ridiculous. I would go through other means to try to find a SOHC/4. I think some of these sellers on ebay are trying to make a living by doing nothing else but flipping these bikes.
Boxnife, I don't dislike any SOHC/4 but the 750 K's 69-76 are my favorite. I don't see how you can say you don't like the 750. I had a all original 1976 CB550 back in the 70's and I really liked it. Of course if I knew than what I know now I would of never sold it, but I still favor the 750 I must because I have 2 of them
It's really bad that your 550 was stole. I hope you find another one. Talk to people, ask questions, let them know your looking for old Honda motorcycles. No telling what you might run across.