The risk of being sued is significantly greater than the risk of being personally liable (See Ready Reference Page: “Directors Often Fear Risks of Personal Liability”) , but the cost of defending oneself without insurance can be hugely expensive.  I would continue to look for coverage.  Since your industry seems to be especially litigious, it may be expensive, but it ought to be available someplace.  Personally, I would not stay on the board if you couldn’t get it.