No sé si esto te sirva:
Inversionista por cuenta propia:
investor who buys securities and commodities futures on his own behalf,not for an organization
Reference Gloss.of Finance and Debt,World Bank,1991
(1)
TERM end investor
Reference OJEC C 325/1991
(2)
TERM retail investor
Reference Gloss.of Finance and Debt,World Bank,1991
Sé que no es exactamente lo que necesitas, pero quizás te pueda ayudar.
List broker: a mediator who executes transactions for one or more users and more than one list holder, either in his own name and on his own behalf or in his own name and on behalf of a list holder or user-client.
Lo que me lleva a que el término correcto es "transactions on his own behalf".