The question is…. Are you allowed to side vent? If so, I would go that route. I have the “mushroom” on top of my trailer but I have more equipment running and also a busy char broiler that produces lots of grease.
I worked movie catering trucks for years, all were side vented with 3 fans. Running a big flat top, ovens and range. We did a weekly wipe down of the fans and the housing, along with cleaning the filters, took about 15 min and cost nothing.
With the top vent, in my neck of the woods they are required to be cleaned professionaly by a hood cleaning company every six months, at a cost of around $300.
Did you look at the wall mount fans on vent direct web page?