Cob: where to get clay and straw

[Theodore Schluenderfritz]

gonna start on a small cob project this spring,

tested my soil and it looks like it doesn't have any clay...mostly silt.

any ideas where to get clay and straw?

(sorry to be such a city kid, but that's what I am...Milk comes from the 
grocery store...what's a cow?)

Thanks,
Ted