I would like to get a few random bits per day from nature (from chaotic physics, like rolling dice, or quantum physics, but not from cryptography) which Alice and Bob can measure independently from opposite sides of the USA. My first instinct is to measure emissions from the sun, or even other stars, but I have no idea what exact emission has strong variation and strong correlation across the earth. I'm aware of all the NASA satellite data, which could be used, but I'd prefer something with "theoretical flip-flop bistability". Does the galaxy flip any coins?
What's a practical (preferably cheap) recommendation? Does anyone already do this?