"There's a pair of scissors." Use that.

There used to be several things in English that were always a "pair." Now we can say the same thing two ways. 1) I bought a new pair of pants. (Originally, each leg of the garment was a "pant." They were even separate legs at one time. This was a long time ago.) Now we can also say, "I climbed a tree and tore my pants." 2) May I borrow a pair of scissors?" (Each blade of the pair of scissors was a "scissor." Now we can also say, "Don't run with scissors!" 3)I got a new pair of glasses (i.e. spectacles). Each lens was at one time considered a "glass." Now we can also say "I crashed my bike and broke my glasses." I can't think of any other examples, but there might be some. You can NOT say: I used a scissors to cut out the pictures. I bought a new pants. I have a new glasses. "Pants, "scissors," and "glasses" all act like plural nouns, so it doesn't work to use the singular "a." with them. You have to use "some," as in, "I bought some new pants." Also, they take a plural verb if they are the subject of the sentence: These sentences are all correct: My new pants are totally cool. My new glasses are really retro. My scissors are better than your scissors.

There are scissors. Generally there would be more than this to the sentence unless someone asked you "Have we got anything to cut this with?", then you might say "There are scissors".