3-wire (Tx, Rx, ground) connection for LCD?

Hello.

I managed to smoke my serial VFD since my last post so i resorted to use smoke an HD44780-compatible LCD.

The device i want to hook up the LCD to has a serial LVTTL port (Tx, Rx, ground) but also has USB ports.

I want to be able to write to it with LCDmod from command line on Debian Linux.

I wouldn't want to buy an USB-to-serial because they cost more than an arduino around here and no online shop ships to my country so the optimal solution would be to use the serial port.

(most serial LCD interfaces i've found are 4/5 cables or 3 cables but they're data, Vcc and ground)

Is there a reliable 3-wire (Tx, Rx, ground) solution to wire the LCD for that serial port or i got it all wrong and i need 2 more wires for voltage and then i should go with the converter anyway?

Thanks for your input =)

EDIT: Why not plug the arduino itself to the device? Well, since arduinos don't come cheap, i was thinking to connect a Shrimp or a Nanino instead and they don't come with USB.