The leader of the circus has access to a rather unique method of transporting through the realms which, if widely known, would have even more sentients trying to get their appendages on it. His method allows him to travel quickly without fuss, as well as move whatever he wants at a large scale at a time through realms.
Putting it simply, if he wanted he could move the entire circus and everyone in the circus down a realm, even if some of the members were in a different continent.
Normally you can only open up a small portal for a small time and there is always the risk of temporal zombies to worry about and other various things. Like the cost of keeping it open, how many can go through, do you want to come out somewhere specifically on the other side, etc, etc. Basically, it's really fricking hard to travel through realms easily, which is part of the circus's attraction really. It'd be like the steam-ships of old times, allowing the chance for people all over the world to see new places which they'd previously have no hope of reaching even one of them.
So to answer your question MM, there are literally billions of ways and devices to travel through realms, but when you consider how large all thirteen mortal dimensions all, billions is pretty much half a grain of sand on a beach. A half grain of sand that's hard to get, normally has a price, a risk and only works for one, etc.
Creatures that live in pocket dimensions find it easier to jump into other planes so there are a lot of other methods that involve jumping into a pocket dimension then out into a different mortal plane. This tends to be more reliable to those that can risk the dangers of these pocket dimensions due to their unstable existences and inhabitants.
-"I'm sophisticated, charming, suave, and debonair, Professor. But I have never claimed to be civilized."