How it used to get handled in Kiting circles was under the relevant Clubs 3rd party insurance then paid for by all members. That Insurance was handled as a bundle Nationally and purchased for a time for any Club wanting to participate. Most events then took some $$ and I am sure that went into the pool toward paying the yearly $$ instead of just the members of that club.
The MAAA (Model Aircraft Association of Aust.) has done that same sort of model for Decades now and has managed to keep the overall cost per member 'sane'.
Where it has all gone wrong in the last few decades in particular is 3rd party for anything close to dangerous has gone off the charts. As an idea way back in the past commercial Bike Hire insurance was sub $1k, last time I got a price there was only one provider left and it was over $5k even some years ago
So if you are chasing one off Insurance or for a small club best of luck,