My buddy uses a real cool one. It is an upside down modified tm type prong rest mounted from the sight holes. A cord is atached to it an the cables - like a drop away. When he loads his arrow on his " regular" tm rest he simply swings the to overhanging prongs to press into the top of the arrow - thus sandwitching the arrow between the two rests - it' s not going anywhere.
When he draws back - the holder swings up and out of the way in the last few inches.

I can take some pics if you like