What do you need insurance for? You re a performer they ve hired; if anything, their insurance should cover any injury YOU sustain in the course of the evening, unless for some reason they expect you re going to harm a guest, but again that guest s harm is covered by their policy because they re the ones who brought you in. It sounds to me like the organizers are pretty new at this. To answer the question, yes you can buy short-term insurance, and it isn t very expensive. I paid about $30 for a $1-million policy when I rented a charity booth at a shopping centre for a weekend. Contact any local insurance broker to make arrangements, but again, you buying one is totally unnecessary.
You can get insurance for a single event. However, my suggestion is that you just get an annual policy. It shouldn t cost more than $300.
