Based on the information supplied there doesn't seem to be any reason you cannot take a standard travel insurance policy so do a price comparison here on Money Supermarket and decide which policy offers you appropriate benefits for a reasonable price.

Hope this helps.

Advice would be welcome. I'm going to California for 10 weeks, mainly to do research in a Los Angeles library.

Is there a particularly cheap but good policy for such a low-risk activity?!

Thanks in advance