We added our bikes to our LV contents policy and it covers outdoors too. We've never claimed and I'm not sure it'd cover that much. There might be a per-bike limit. I should probably check...
Every time I've looked at insuring bicycles against theft or damage, the cover available has been either completely useless for nice bikes or so expensive that you're better off self insuring.
https://youtube.com/watch?v=oavMtUWDBTM