"Cowboy chords," if I understand what he's saying correctly, are:

These chords are, in order, A - C - D - E - G

e |--0----0----2-----0-----3----|
b |--2----1----3-----0-----0----|
g |--2----0----2-----1-----0----|
d |--2----2----0-----2-----0----|
a |--0----3----------2-----2----|
e |------------------0-----3----|

Try songs by Creedance Clearwater Revival... most of them only use 3 or 4 of these "cowboy chords."