Obituaries that have appeared in Contra Costa County newspapers prior to 1995 are available on microfilm at the Pleasant Hill Library. See this link for specific historical newspaper holdings by communtiy.
Anyone may search the Contra Costa Times' Obituaries page on their site. (Death notices and Guest books remain online one year.)
Local genealogical societies may have volunteers willing to help you locate Contra Costa obituaries.
Please note that due to budget and staffing reductions, Library staff is no longer able to perform obituary searches on behalf of patrons, nor respond to obituary requests from non-Contra Costa County residents.