There is no such thing as an influencer marketplace or platform available. For now, the best social media for finding NFT promoters is Twitter. Here you will encounter a lot of promotions, giveaways, and shilling from different Crypto and NFT projects. These promoters usually offer other services on other platforms, but Twitter is the crib of crypto promoters at the moment. YouTube has some relevant promoters that are also worth taking a look at. The best way to make sure that a promoter is legit is by looking at websites such as Social Blade, where the promoters receive a score based on the engagement that they have. However, it is always important to do your research. For example, an influencer on Social Blade might have a low score because of his low engagement, but maybe that low engagement is full of potential buyers. Quality is more important than quantity.