concession hunter; profiteer
A person who seeks to profit from political or business concessions, often with a negative connotation of exploiting connections or privileges.
As a concession hunter, he quickly gets hold of bidding information for public works projects.
Profiteers swarm around that politician.
死の商人 (merchant of death) refers to arms dealers or those who profit from war, a more extreme and specific term than 利権屋.
Compound of 利権 (concession, rights) and 屋 (person engaged in a trade or profession). The exact historical derivation is uncertain, but the term likely emerged in modern Japanese to describe those who exploit political or business privileges.