Praise be to Allah, and may Allah’s peace and blessings be upon the Messenger of Allah, his family and his companions.
To proceed:
There are many scholarly opinions regarding dealing with people whose money is predominantly unlawful. The most notable of the opinions is that it is permissible. This includes accepting gifts from them. This is indicated by a hadith established on the Messenger of Allah (peace be on him) which was transmitted by Bukhari (2933) on the authority of Abu Huraira (may Allah be pleased with him) who said: “When Khaibar was conquered, a (cooked) sheep containing poison, was given as a present to Allah's Apostle.” The present came from a Jew but the Messenger of Allah (peace be on him) accepted it despite the fact that Jews eat unlawful things and most of their money is interest related. This opinion is also supported by a hadith transmitted by AdulRazaq with a sound chain of narrators in his Musnaf on the authority of Abdullah IbnMas’ud(may Allah be pleased with him) who said that: “A man asked him: I have a neighbour who eats interest and he keeps on calling me to eat his food, he (IbnMas’ud) responded: accept it and the sin is on him.” A similar narration was mentioned on the authority of Salman who said that: al-Hasan was asked concerning the food of the money changers and he responded: Allah informed you that Jews and Christians eat interest but made their food lawful to you.” All what has been said is with respect to receiving the gift directly from the person who deals with interest. However if someone gets the gift through a lawful means and gives it you either as a gift or as a result of a transaction as the matter in question, then accepting it is permissible and there won’t be any sin on you. Nonetheless, you should not accept the gift if accepting it involves advertising and promoting of unlawful things or leads to people being confused about the ruling.
And Allah knows best.