It's not always possible, but you can sometimes find 'non-dedicated venues', in places that aren't really intended for that purpose.
I used to run a few outdoor car rallies at places around the English West midlands, Weston Park, etc.
These, of course tended to be in the 'middle half' of the year, for weather reasons. It was suggested that a mid-winter event would be a worthwhile thing, if we could find somewhere 'indoors' that was viable.
I had a bit of leverage at the local RAF station, which turned out to be very efficient leverage, and they agreed to provide us with a large shed, by driving the wagons stored in there outside for the day.
Amusingly, given the state of my passport and the fact that the first event took place on the day before the launch of Desert Storm, I was entrusted with the 'security' for the event - this went as far as me being given three armed squaddies to scan the entrants and their vehicles, once I had identified them as verified entrants*.
There were a few people I considered having bumped off, but it would have looked bad in the rally report.
Anyway, the point is that a bit of thought just might come up with a viable alternative...
*There was a small 'alert' when one on the Morris Travellers approaching was not on my registration list, and the chap driving did not have the paperwork I would have sent to his home address, had he been a 'real entrant' - he did however offer me a 1250, an RAF ID card - not knowing him, I didn't read it properly and just called the corporal over with "I think this is one of yours!" - this turned out not to be standard procedure, as the driver was the station CO...