I’ve found both browns and black widows in our tiny flower gardens at two different California homes.
You know that canned air we buy at Staples to clean our computers?
That’s what you need. Get a good angle (after a test spray to get the can cold) then spray that bug until it is frozen solid! It works almost instantly. Those legs curl up tight. Frozen spiders are MUCH easier to squish. Or you can drop them into ice cube trays and save them for Hallowe’en… just remember, where there is one… there are others.