Is there any kind of accidental drift/spraying insurance?

You really need to talk to your insurance agent and ask them if you have that coverage, a lot of the time you may need to add an “endorsement” to your farm owners policy. Generally this protects you against drift to crops “other than yours” from your premises; however if you are doing the spraying as custom work that may not be covered from your farm owners only policy, you most likely will want a commercial policy. I would suggest you ask your agent to show you, (in your policy) where this coverage is afforded, not just tell you it is