"Are there monitors available that works on serial port?"

Serial interfaces on computer monitors are not used for the purpose you're probably interested in. They are typically for monitor adjustment or for touchscreen information.

If you only need to display characters, the CRT (monitor) section of a character terminal might suit your needs. If you need to display graphics, graphics terminals are also available, but at higher cost. A terminal is as close to a "monitor with a serial interface" as you're going to get. Any system with a serial port can have a character or graphical display by using a terminal.