Consider hiring a marketing agent
The job of a marketing agent and a contract advisor are two very different ones. Contract advisors are used to dealing with teams, a situation in which decision-makers are well known, player contracts are a business necessity, contract details are public information, and there is a salary cap structure, including salary minimums in place.
Because this is a rather involved situation, many contract advisors are simply not equipped with the experience or time available to devote to marketing. The marketing business is different.
There, decision-makers are hard to locate, contract details are protected by non-disclosure agreements (and are not public information), player market value is extremely subjective (no salary structures or minimums), and athlete endorsements are definitely not a business necessity. Many of the most marketable players in the NFL keep their agent work and marketing separate for this reason.