At minimum, I'd buy a monopod that either telescopes or breaks down into pieces. Even better if it has a ball head on it.
Frankly, the best 'trick' I can suggest for getting the complete show in the best quality is to suck it up and take a tripod in. I don't say this lightly because I know it takes balls and sometimes doing this type of thing isn't for the faint of heart. OTOH, from personal experience, most festival bouncers are simply looking to keep beer/booze out of the festival grounds and not much else. Venues are different, but festies are usually so much less strict.
I'd say that 95% of the time or more, you're not gonna be called out if you have your camera set on a tripod, especially if it's nighttime and you don't keep your video screen shining brightly. My thinking is that, if I can get a good steady video 90% of the time or more, but maybe 1 outta ten times I get asked not to film, then I'm WAY ahead of the game and much better off losing that 1 outta 10 show than having 10 outta 10 shaky handheld shows. That's just my way of thinking...but I've been recording for years, so I'm pretty bold when I walk through the gates.
Having an attitude like you're on a mission and that you're entitled, while it might not get you anywhere in the end, usually gets you where you need to go.
I'll give you an example...I don't do much video taping anymore, but several years ago I video'ed a ton. For two consecutive All Good festivals, I video taped almost the whole festival from my home camera set on a tripod that was standing right next to the SBD...10 feet to the right of it in plain view. Since I was there day and night, I kinda think by the time it was over that most everyone thought I was filming in some kind of official capacity! LOL.
Use Jedi mind tricks and don't be timid or shy about carrying your stuff in with you. After setting up, if you do ever get called out, just claim ignorance and comply. Take the camera down right away and be compliant and non-argumentative and even apologetic. If you try and argue, you're setting yourself up for bad things to happen. NEVER and I mean NEVER allow anyone else to put their hands on your gear. Just walk away without saying a word if you have to, but don't let them touch your gear...chances are good that you won't get it back if you do. At the very worst, give up a tape, but not your camera.
BTW, in 20 years of recording audio and video, I've only had 2 times where I had to walk out and only once where I felt where my gear might be in jeopardy...and both of those times were a long time ago so there's likely nothing to worry about. I'm just saying IN CASE you ever encounter these situations.
EDIT: I just re-read what I wrote and need to clarify. Be bold, but don't be stupid. I'm not suggesting that you should walk right in with all of your gear in plain view. If you can stash it, then do it (hint...camp chair bags are great for stashing a tripod). My point is that when you go through the gates, do it with a purpose and don't be shy about being a little aggressive with the people about telling them you have absolutely no beer on you and they're free to search you head to toe if they want. Usually they just wave me through. Another hint is that, IF they stop you and keep your from bringing your stuff in, you can usually set it on the ground nearby (say near a fence that has a gap at the bottom) and wait around until they're distracted. (Lotsa winks in the above paragraph.)