Primary sources

A .pdf copy of The Heart of Great Perfect Wisdom Sutra as well as The Four Vows is available here.

A .pdf copy of Genjokoan, translated by Shohaku Okamura, is available here.

Recommended books

Meditation: Now or Never by Steve Hagen. More information available here.

Practice supplies

Two sources offering zafus (cushions) and zabutons (mats) for sale are:

                     Dharma Crafts

                    Carolina Morning