I'm giving this a nudge over to the Power & Illumination board, since that's a better fit for general preparation questions. We don't generally have shopping directories on the board... what immediately comes to mind, other than 'use a search engine to look for companies renting equipment in NW Nevada and contact them'
would be to reach out directly to contacts at the camps you've seen renting the kind of big equipment you're looking to rent. Second, if you're a part of a camp that's been a registered theme camp in the past, you may want to get with your theme camp's coordinator and see if they have any of the placement emails from last year. I'm almost certain that there's something mentioned in at least one of their newsletters throughout the season, if memory serves it's in early summer. You may also want to check with Outside Services (you can reach them using the firstname.lastname@example.org
address), since any outside service providers would need to be registered and go through them.