Technically, this phrase should be "there are a few" or "there're a few". However, this is a common mistake that English speakers make in spoken English.
Some people make this mistake because they don't know whether a verb is supposed to agree with "a few" or with the noun that follows it:
There's a few people here already.
There are a few people here already.
Other people know the rule but forget while putting sentences together in spoken English.