What kind of countertop are you looking for exactly? Formica? Wood butcher block? Painted? Acrylic? Aluminum? Trying to blend in with existing cabinetry or stand alone/contrasting?
Home Depot sells Formica tops. Floor and Decor sells wood butcher block blanks. Plasticare sells acrylic. It depends on how much access you have to tools and your comfort level with doing the work yourself. Budget also effects the final product.
If you have some specific ideas, it might help us help you find a solution. Otherwise the sky is the limit.