Home Depot or Lowe's are probably your best bet.
Go to the kitchen cabinet department and tell them you want laminate designed for a vertical surface. They may act completely confused. If so, tell them you want Formica (Four-MIKE-Ahhh). They will point you to a rack or box with 3000 color chips. Tell them you want black. They will show you 80 samples that are dark with various spots and flecks of color designed to look absolutely nothing like black granite or black marble. Tell them you want basic, one-color, flat black. They'll lie and tell you it doesn't exist. Give them the finger, walk over to the paint department, grab some primer and then start the whole process over again by telling the paint buy you want to buy some black paint...