Here is a simple USB lamp powered from the USB socket of PC. It uses 5mm high bright White LEDs to give ample light to work in the Keyboard if the room light is not sufficient. No PCB is required to make this circuit.
The circuit is too simple and can be wired through lead-to-lead soldering. The LEds are connected to current limiting resistors R1 through R4.The cathode of all LEDs are joined together and soldered to the black wire of USB cable. Free leads of all the resistors are joined together and connected to the Red wire of USB cable. You can use a discarded USB cable with Class A type connector. Cut the Green and White wires of the USB cable and use only Red and Black wires. USB socket of PC provides 5 volts so that the LEDs give bright light. LEDs can be fixed in the Key board by drilling 5 mm holes.
Class A USB Connector