Best is to remove the worn wafers, probably only one or two, and reassemble. No new parts needed.
Find the YouTube video: 2003 Honda Odyssey ignition sticking. Shows you just what to do.
You can replace the cylinder, I think you have to purchase a cylinder/switch assembly. However, a new cylinder means a new key, and your immobilizer system will not recognize it without reprogramming. If you are handy with tools, it's easier and cheaper to just remove the worn out wafers, put a little lithium grease on the cylinder, and reassemble.