I'm not sure about the sub-panel, but I personally booked electricians in Los Angeles here https://brentwoodelectricalexpert.com/electrical-panel-upgrade-service/. Just a service to upgrade the electrical panel. I think they can help with the sub panel as well, so feel free to contact there. I think you will enjoy working with them, I personally liked it.
Need to upgrade your electrical sub-panel?
I'm not sure about the sub-panel, but I personally booked electricians in Los Angeles here https://brentwoodelectricalexpert.com/electrical-panel-upgrade-service/. Just a service to upgrade the electrical panel. I think they can help with the sub panel as well, so feel free to contact there. I think you will enjoy working with them, I personally liked it.