Is it permissible to return a lawyer's gift, then buy it from him, in order to avert the suspicion of embezzlement, especially since the Prophet (peace be upon him) warned against gifts to employees?

A gift given to an employee because of his job, which would not have been given to him otherwise, is not permissible to accept because it is a bribe. Umar ibn Abd al-Aziz said: "A gift in the time of the Messenger of Allah, peace and blessings be upon him, was a gift, but today it is a bribe," meaning gifts to officials. If there are dealings between you and the giver by virtue of your job, then it is more pious to avoid accepting the gift altogether. It is permissible to buy it from him for its equivalent price if he is selling it.