Please keep in mind that there is no such thing as perfect competition in the real world. However, I would say that the closest thing to the situation you describe would occur in the market for various kinds of farm products.
The factor market for these products includes such things as farm labor and fertilizers and seeds. All of these things are commodities that are relatively competitive. They are not all perfectly competitive, but at least the labor market is quite close.
The product market for agricultural goods is about as close any market ever comes to perfect competition.