“Informational copies” of a death certificate can be purchased by any member of the public from the County Clerk of San Luis Obispo County, California (or via VitalChek Network online).
It is not necessary to state the full reason for your purchase, such as an inquiry into Obama, as inquiries are commonly approved for non-family members for other reasons such as “real estate title research”.
The current fee schedule asks $12.00 for copies ordered directly from the county (VitalChek may add transaction fees).
San Luis Obispo County Clerk-Recorder
1055 Monterey Street
Room D120
San Luis Obispo, CA 93408
(805) 781-5080
http://www.slocounty.ca.gov/clerk/CopiesofVitalOfficial_Records/deathcertificates.htm
The San Luis Obispo Tribune may have also published a death notice or obituary sometime after June 19, 1980. This could be located at the main library in San Luis Obispo.
There is a rootsweb list where volunteers will do lookups (live nearby and go into the court house) CA-DEATH-INDEX list. He's not in the archives as having a lookup requested. What would it tell us that would be relevant? Somebody looked one up for me in Santa Clara County, and it gave name, place, DOB, death date, cause, mother's maiden name, father's name, birthplace, disposition of body, can't remember if there is anything else. Nobody has requested a search on the death index list on that name.
You can write most libraries, and for a small fee, get a copy of an obit, but I doubt there is one because there are lots of different papers to search plus it doesn't sound like he left any survivors.
His probate records might be there somewhere, too, even if he died intestate.