I used to attend computer shows in N Calif, attended my first back in 1985 and bought all the parts I needed to build my first PC.
However, I'm not aware of any shows still being put on. I suppose the ability to easily find and compare components on the internet has killed attendance at the shows. One show I attended regularly was held at the local fairgrounds so you might try contacting the local fairgrounds to see if there are any shows on the calendar.
Not sure where you are in N Calif but there is an electronics swap meet I'm aware of that is held at De Anza college in Cupertino on certain weekends. It is oriented more toward amateur radio but I believe you can find computer components as well. Here's a link: Electronics Flea Market