You can buy a giant LED from a guy who makes them at home. The cost about $70.
From his site:
My first Maker Faire as a maker was New York 2012, I brought a Giant Arduino Starter Kit (YouTube video Giant Arduino Starter Kit – A 10x Scale Model). Everything was ten times scaled up; the Arduino Uno, breadboard, resistors, potentiometer, LDR, jumper wires, and LEDs.
As the LEDs were portable, I would bring an LED with me to other Faire's, it has always been received well and many times people would ask was it for sale.
In September 2018 I decided to explore turning the rough model in to something that I would be happy to sell. The following YouTube playlist records some of the progress in Making a Refined Giant LED.