Hes already got an inflatable that he uses...all his races start and end at the exact same spot.....Im guessing he is trying to keep from dragging out a genny to keep the inflatable working all the time and leaving the metal structure up....just a hunch.
I forwarded your request to a friend of mine, Freddie Sheppard. He would know of any used ones and/or could build you one. He has built a lot of this kind of stuff for Supercross and Monster Jam.
He is not on RDC :-(
Tomcat sticks are overkill for what he's doing. Even then Cash Landy may have something used. What he needs doesn't have to be load bearing like squint or roof truss. This goes up at a ranch where they race UTVs. If he's not going to move it a more appropriate solution would be to install it using structural tubing and steel.
I noticed the Vegas Rigg Knack box in the shots with your dog. I've hung my share of shows though I'm able to breath through my nose and not have to wear Band Aids on my knuckles. DOH!! Just kidding. I breathe through my mouth...
Audio is/has been my primary gig. Worked with kats like Harry Donovan, Joe Branam and Rocky Paulson when I was touring and doing corporates. I moved to this fine metropolis when I got tired of touring. These days it's a cushy house gig with a few corporates, sports and TV thrown in here and there.
The OP probably can afford something more like one of those McMansion/ county horse lot archway gates than new sticks of truss. Unless you can get him the killer deal on something used. That's why I'm saying it looks more like a wrought iron type project painted to look like truss than an exhibit or temporary structure. I don't think he needs to move it. From how those are used on other events I think it's only got to be load rated for the span of the members.