He should apply to the UC’s and the privates in California, seeing as how you are a resident.
The FA departments at the UC’s have ways of finding private scholarships. If your son is a National merit winner, he can apply to USC-they like the NM winners and will fund them. (Harvey Mudd and other privates have funding)
We also live in California and the offers of funding, for our high stats son, were impressive. With Covid, I don’t know how that will change.