The name I have seen for these the most, is Gobi desert agate. However, not all are agate, and not all are from the Gobi desert.
However, a search on Ebay with this name should yield some results.
And....to easy your mind: I have not seen these in Tucson last year, and would be surprised to find them this year. I will look for them though.

Edit: obviously, these pics are not the Desert agates........My mistake.