How do I obtain a relic of Cora Evans? I understand her cause has been opened for canonization.
You would need to contact the diocese in charge of promoting Cora Evans's cause, which is the Diocese of Monterey in California. Someone there may be able to provide third-class relics (which are materials, usually pieces of cloth, that have been touched to a saint's body). Keep in mind, though, that most dioceses these days will be unlikely to grant first- or second-class relics, in part because of this provision from the Code of Canon Law:
Relics of great significance and other relics honored with great reverence by the people cannot be alienated validly in any manner or transferred permanently without the permission of the Apostolic See (can. 1190).