You can get white/proso millet at feed stores or even wild bird stores. Cheapest at feed stores, though! You should be able to get several pounds for under $20, I can't remember the exact price I paid.
To get the hot temps, get slate rocks (not black) and position a heat light on them. Use a light fixture with a ceramic end to it as the plastic will burn out more quickly. Get a 125 watt heat bulb from Home Depot. It's the kind used in bathrooms to keep you warm after a shower. Get the clear one, not red. Works great! You may have to adjust the angle or the height of the fixture or the slate tile.
If you use a Mercury Vapor Bulb, be sure to follow guidelines on how far away it should be. Same for other UVB lighting, it needs to be within a specific distance or it doesn't work.
Good luck!