Wow, nice score! Yeah that's a shorter wheelbase race kart that are usually referred to as a "Kid karts" by the racers. I'm not sure what brand your chassis is but its older nerf bar design was discontinued by most all brands sometime around the early 2000 era so I'd say you probably got a 1990's model there.
ps: If you want to find an air cleaner from a local source you could measure the diameter of your carbs air cleaner mounting flange and probably find and buy one from a motorcycle shop. (they just slide onto that flange and are held in place with a hose clamp)
Many tracks still allow the older design chassis to compete but some dont. I'm guessing they'd still allow it in the Kid kart class but you'll have to check your tracks rules or contact their Tech director to find out for sure.
ps:
If your going to race it, double check to see if they require any special types of air cleaners. Some tracks/classes require enclosed air boxes to help lower engine noise.