So I just bought a used St. Croix LTB rod and while fishing the top guide I am not sure what it is called but the black part in the eye fell out and was rattling so I just went to put it in pocket and finish fishing the day and of course I dropped this piece on the dock and lose it. Just my luck lol, So does anyone have an idea of where I can buy this piece and how I can replace it myself or suggestions on where to go to have someone fix it for me? Doesn't seem to be too big of a deal I just have no experience with this type of issue. I attached a google image photo my tip is perfectly fine just the black part in the guide fell out and I no longer have the piece as I said above. 

you will need to buy a new tip top.  with out the insert it will fray your line.  you can buy a quick replacement at BPS or even order a new top from st croix for a few bucks.  it should not be too tough to fix your self.

Yep just re tip it.The glue and tip kit only costs a few bucks.Heat the tip up a LITTLE bit go get the glue warm enough to pull off and put the new one on.