I ran into this problem 4 years ago for a wedding at an american wedding hall. I called some insurance companies from Long Island, (can't remember now, the hall gave it to me) and they wanted $600 for a one day event. I ended up telling the bride to find someone else because 99.9% of the restuarants and halls we play in, do not require it. It came down to that this is really just a part, part time for me, I only do about 12-24 parties a year and the investment was not worth it.

btw, it worked out to be cheaper if you buy the policy for entire year.