They’re $3 in the party/card section at Walmart. The handle is 4 1/2" long which means the dome is about the right size for a giga meter.
Sure, the colors are a bit off but you could snip off the blue LED’s. 
For reference:
That looks great! And for only $3, I can butcher a few trying to make a proper giga meter! 
i actually posted these finds about 2 years ago from same place, but they were $1 at the time. GOT DAMN Economic inflation!
Yes they work well…