How To Get The Most Renegades Coins

On high levels you're pretty much restricted to the Oblivion parts of Temple of Time or Future Henesys, from what I could tell the monsters either need to be 150+ or within 10 levels of you.

At the very least I've seen them drop from all the monsters past the Door to the Future Area, and my buddy list tells me the Road of Oblivion maps drop the pieces too, though I haven't checked those myself.

It's definitely 150+ if you're 161 (or higher) or over. I got one while going through Qualm Monks on my NL.