You haven't said whether your deceased parent was in a close relationship with another person withwhom the parent might have held accounts jointly. If so, the accounts may have passed automatically to that person upon your parent's death.
You might try the unclaimed property section of the California state government and you might try going to various local banks where the deceased parent lived. If you show a death certificate and your identification the bank MAY tell you if they have an account in your parent's name. It is very unlikely they well tell you the amount. But if you find an account, you can then initiate a probate proceeding to order the bank to turn over the information.
You can check with every employer and organization your parent was associated with and see if they have any record of life insurance.
These are just some suggestions to get started.