Hi,
i hope that could help. Yes, there is some institutions that will do a credit line equity on your manufactured home. I am not sure in California, but here an example:
https://www.twinstarcu.com/home-equity-loans
Primary Residence - Over 80% Loan-to-Value (LTV) on stick built homes. Manufactured Homes must be new or last 9 model years and limited to 80% or less LTV. Must be classified as real property & located on land in the borrower's name. Value is based on tax assessed value and verified by independently certified valuation; or full appraisal; member pays cost for appraisal. Value method and cost determined at time of application. LTV over 80% is an exception and requires additional review and approval.
I have no affiliation with them and used them to show you that there is hope :-)
Contact Credit Union, i think you will have a better chance. Also, manufacturers of mobile home can be a good place to ask, they often have agreement with local lenders.