The only separate component that will handle HDCP is called the
HDFury. This basically takes a digital/HDCP protected signal, performs the necessary HDCP protocol mumbo jumbo, and then converts the digital signal to analog to be output over a VGA connection. With your current plasma screen, you could pipe HDCP content into your VGA input using the HDFury.
I don't know of any way to properly handle the HDCP mumbo jumbo and maintain the digital signal for your display.