If I'm wrong my apologies here but a "shill" might be more in line here. Definition of shill according to Wilkipedia;
"A shill is a person who helps another person or organization to sell goods or services without disclosing that he or she has a close relationship with the seller. The shill pretends to have no association with the seller/group and gives onlookers the impression that he or she is an enthusiastic independent customer. The person or group that hires the shill is using crowd psychology, to encourage other onlookers or audience members (who are unaware of the set-up) to purchase the said goods or services. Shills are often employed by confidence artists. The term is also used to describe a person who is paid to help a political party or other advocacy organization to gain adherents; as with the situation of selling goods or services, the shill gives the impression of being unrelated to the group in question, and gives the impression that he or she finds merit in the ideological claims of the political party."
