Well, if it is illegal, I would not recommend it... but yes, Microtus will live quite happily on alfalfa pellets, supplemented with a bit of greens and a bit of hay. We cropped the hay to 3 inch sections with scissors, and they both ate it and nested in it.
But they are smelly little creatures, and they are much more disturbed by cage cleaning than are the usual mouse.
We have a vendor at our local herp show that sells African Pygmy mice. They are quite tiny, and look like miniature Deer Mice. She says the pinkies are the size of a large ANT.
