Fifties Primetime at DHS, outdoor bar's near streets of Hollywood at DHS, Bar at the Poly, Kona at the Poly are some that come to mind. Probably most of the hotel bars. I have a drawer full at home from over the years!
I second EBay .... I bought a dozen several years ago and gave them out as favors for my son's 5th birthday party. They were a BIG hit, and not expensive. I think they were called "Lightcubes", or something to that affect.
Ive bought them but the ones they out in the drinks are a bit different and I like those better. It's very nitpicky stuff but they have smoother edges.
You can also get them off the cupcakes where the Osborne Lights are right now.