Who Collects The Collector?

Finish the "Sisterly Love" mission first, then head to the central Spendopticon area - just south of the main part there's a random-spawn spot that produces an Ice Loader, a Shock Loader, a Hot Loader or the Debt Collector. You may need to quit and reload several times to roll the Debt Collector; it's a big one, walking about on its own. Once it spawns, kill it.