Sorry to hear about your cat problem. It took me right back to the days when I was boarded for Summer Stock at a local resident's house who had 8 cats and all of them used every surface as their litter box....thankfully my room was exempt from that as it had a door.
Are you in an open air booth right near the audience or are you closed off? If you're in the open, it's harder to recommend any cover up solutions because some people have nasty reactions to scents that are that saturated.
However, if you're closed off, To cover the odor in the immediate: I would suggest an air wick fan (the tiny ones you plug into an outlet that use scented oils). They can sort of cover up the smell of cat urine. Any Oust spray product should work out ok too, however you can still sometimes smell the cat pee through the cover ups making a nauseating ocean breeze smelling cat pee...But you could certainly do much worse than those two products.
To Eliminate: I use Nature's Miracle (Advanced Just for Cats) for everything our cats do (hairballs, puke, pee etc etc) and with two cats in our tiny one bedroom apartment, you can't smell them at all except when you stand in front of their litter box. Has a lighter smell than most cleaning supplies I've used, and so long as you can find the spot the cat has decided to use as its bathroom, you should be able to eliminate the smell eventually. It's not exactly the fastest working solution, but I've had cats for my entire life and the fact that this works at all, is a wonder. You can get it at most pet supply stores and a 24oz bottle is about $12. (Here's the link to it at Petsmart:
http://tinyurl.com/2vco5nl)
The elimination is obviously much easier if the booth isn't carpeted....just as simple as making sure you get into the cracks of the tile or hardwood floor. If you are carpeted, make sure you let the spray penetrate deep enough before you try to wipe it clean. Good luck!