I've had good luck getting quinoa at my local grocery store or the local food coop. I've gotten millet at the coop, but I haven't tried malting any, so I don't know for sure if it would.
Also, great luck with buckwheat from my coop.
You'll probably just have to see what is available in your area.
Further note: I had asked for advice on sprouting grains from a local 'raw food' person, and they told me that they had bad luck finding millet that would sprout. According to them, it isn't as 'durable' as other grains like buckwheat. They said it needs to be really fresh, and to start out soaking it for only a few hours, as it drowns quickly, especially if it is hulled. Keep in mind, of course, that this information is second hand, and from a person who plays guitar on the street and doesn't wear shoes...