If you have an LDS account you can request a copy from LDS.org. Under My Account there us a Patriarchal Blessing section.
Patriarchal blessing requests are now done online, there is no longer an office for that at the COB. You will need to use your LDS.org account to sign in here: pb.lds.org/pbrequest/ If you don't have an LDS.org account, ask your ward secretary to help you set one up.
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