Bath and Shower Seal

Hey guys.
Ok basically we're looking to get our hands on some black plastic sealing for the kitchen. The countertop is black as are the wall tiles and all i seem to be able to find is white and cream seals.
Ive googled and looked around but just cant seem to find anything useful.

Does anyone know if its even possible to get back seals?

The stuff we want looks something like this



but any variant of the same idea would do. Its really just to stop water getting down between the wall and the countertop at the back.