Is there a pink gum filler of some sort to hide the black bit around my gum line or is it a renewing of the crown needed?(photo)

Best results would be to reshape gum line first so that it is symmetrical and then do a new crown.  More pink will not look better but worse.

From your photo , it appears you are concerned about the left front incisor.  How long has the area appeared darker?  Is the right one also crowned? Unfortunately any gum colored restoration would effect the integrity of the margin of the existing crown and would basically be a drilled filling at the gum-line.  It may even make matters worse. If you were my patient I would caution you about the next step and be sure that it is what you really want. If so I would recommend an all ceramic (non-metal substrate) replacement crown.  Furthermore since the present gum-line is not identical to the right front , I would adjust it prior to impressions at the time of preparation and temporary crown insertion.  Be sure this is what you really want, because if the present crown has a good fit..you are going through new treatment solely for appearance ( not that this is wrong..but both you and your cosmetic dentist should know why!