I am using this 4x20 character backlit screen ($25) available from Digikey (p/n NHD-0420D3Z-FL-GBW-V3) or Jameco.
The Opto22 serial adapter is plugged into a RS-232 to TTL converter, Jameco p/n 2157845 ($10). There are other converters available from Digikey that are more expensive but might be more reliable.
The operation is easy, just send a few characters to set the cursor position, then send the characters to display. There are commands to clear screen, set backlit level, and create custom fonts.