Where can I find the "Oath of Membership" for new Auxiliary members?

The "Oath" is the pledge for new members.  It is available in figure 3-1 on page 3-11 of the Auxiliary Manual, COMDTINST M16790.1G: 

Prologue and Pledge for New Members

The pledge you are about the take is your commitment to support the United States Coast Guard Auxiliary, an organization dedicated to the promotion of boating safety and providing assistance to the United States Coast Guard in the fulfillment of its civil functions. You accept this membership as a volunteer, and as a member you are charged with certain responsibilities and obligations. These include your willingness to support the Coast Guard Auxiliary and its purposes, to faithfully execute your duties, and to participate in its authorized programs to the best of your ability and to the extent that time and circumstances permit.

As an Auxiliarist, you enjoy certain honors and privileges, among them, wearing the Auxiliary uniform and flying the Auxiliary Ensign. Wear the uniform neatly and correctly and fly the Blue Ensign proudly. Remember that your conduct reflects directly upon the image of both the Coast Guard and the Auxiliary.

The satisfaction you derive from your Auxiliary membership will be in proportion to your level of participation in the organization‘s activities. The success of the Coast Guard Auxiliary will depend upon the extent of your participation and upon the quality of the Auxiliary leaders that you, the member, select.

(ASK THE AUDIENCE TO RISE)

If you feel that you can be an active and productive member of the United States Coast Guard Auxiliary, please raise your right hand and repeat after me:

“I, (your name), solemnly and sincerely pledge myself to support the United States Coast Guard Auxiliary and its purposes, to faithfully execute my duties, and to abide by the governing policies established by the Commandant of the United States Coast Guard.”