I had a moving message board (together with around 14 of its identical mates) - the last one went a few months back.
It didn't have a built-in countdown timer, but it did have a real-time clock feature, with timed announcements, so you could program it to display 59 at 11:59:01, and 58 at 11:59:02...etc,etc,etc...
The last time that I had a large countdown display for NYE I had to improvise...
*) Take one ordinary household(ish) radio controlled/sync'd LCD clock with countdown feature or HH;MM;SS display.
*) Illuminate the clock face well, using a 15watt pygmy bulb, diffused to soft illumination with a sheet of A4 between it, and the clockface.
*) Take one home Video camera and point and zoom it onto the clock face, so the clockface fills the screen.
*) Connect live output from the video camera to the largest TV that the venue offers.
*) Add large cardboard cutout to hide the TV, but leaving the TV screen untouched.
Blue Peter? Eat yer heart out...