SKB's thread is excellent! (The one Cypher linked). I forgot to add that scrambled egg goes down well sometimes as well. Erin's Hamsters also has a video on feeding elderly hamsters.
https://www.youtube.com/watch?v=j8JLI7ghwLA
I also did a video on our cage set up for an elderly hamster if that helps
https://www.youtube.com/edit?o=U&video_id=NIxHqvr9wTY