Where can I buy a clear plastic umbrella (not online)?

It’s raining a lot and I want one of those cute clear plastic umbrellas – the kind that are very round and form a dome over your head so you stay dry. You can buy them on Amazon but I’m wondering if anyone has seen them for sale in a specific store so I could buy one here now while it’s raining, rather than order it online and wait for shipping. I live in San Francisco and don’t have a car so most of the huge box stores are not an option.