Backup childcare due to daycare closure

My kids' daycare had a closure last week due to COVID. Thankfully it was a child who wasn't in my kids' classes, and it looks like no one else got sick. I got my kids tested immediately and they came back negative, and I've been monitoring our symptoms at home and had them tested again on Sunday and thankfully negative. Our exposure was minimal since the kid's family kept them home most of the week, and I think the family with the sick kid got the positive COVID test a few days later and notified the school.

Hopefully this was a one-time event but I have to face the real possibility that school closures could be our reality this fall with the Delta variant circulating.

I'm happy to take care of my kids on occasion for sick days and understand the importance of social distancing, but I'd like to ask the rude question of finding backup childcare arrangements for this kind of closure, when we had minimal exposure at school and we need a vaccinated person to help us out with childcare due to an unanticipated school closure. My husband and I are both full time workers and the demands of our jobs make this unsustainable if a closure happens often while we're waiting for the kids' vaccines.

So ideas for finding a backup sitter we can call on occasion? We unfortunately don't live near family, so that's kind of out of the picture. I called my friends to see if they have ideas. If it helps, I'm in the Bay Area so there might be local websites that could support that kind of thing.