I have seen a voucher for a discount for the Adventuredome plus other stuff at Circus Circus in front of the Country Market in Baker, California (very close to the World's Largest Thermometer).
The same voucher also mentions the "Win Cards" (which involve Non-Negotiable Chips for some of the table games -- Blackjack, Craps and Roulette), so don't forget to do them (they offer both $15 for $10 and $30 For $20 -- you get them at the CC Slot Club Booth -- actually you get a voucher to take to the Cashier and then pay [if you want both of them] $30 and you'd get $45 in Non Negotiable Chips which can be played over and over again until you lose them. If you win, you are paid off in real chips and you never have to bet any of them. And so once you have run through the non-negotiable chips, you could actually just get up and leave since you are not obligated to play any more.
Otherwise, you might find something with other vouchers maybe by the bell desk at some places (Las Vegas Club used to have racks of vouchers by the Hotel Registration Desk -- I miss that place). Maybe try El Cortez and Four Queens as well -- or maybe some of the other MGM/Mirage connected casinos to see if they have something.
Enjoy!
RecVPPlayer