Which online vendors send seeds of Andean root crops to the continental US?

Maca seed here, http://www.mountainroseherbs.com/seeds/s eeds.html
As for the rest nearly impossible to get ahold of, you might try contacting these folks, http://www.cipotato.org/cip/global_conta cts.

The Parable of the Besao Gardens

Thirty-four year old Nanay Fidela, pregnant for the fourth time with her three children spaced less than two years apart, makes it a point to include vegetables in her children’s meals. While the market is very accessible to them, family finances have to be stretched for her to purchase what she wants to prepare for the family. The small lot beside their residence was utilized as a compost pit from where the fertilizer she utilizes comes from. The family lives in a boarding house located at Kin-iway, Besao. Fidela planted assorted vegetables in empty softdrink containers, tin cans, tires and plastic bags arranged creatively around their boarding house. Having no wide lot of her own moved her to innovate on how she can come up with a garden.