I looked into the trek years ago when ds was a baby and was told by someone at Pari that the Trek didn't have enough psi for tobi. And I have heard from some that treatments seem to take longer with the trek. When we had a pari proneb and it wore out, tobi took 45 minutes...
I have used a pari vios and proneb ultra in the car with a cigarette lighter adapter and our Jeep and VW Jetta both have regular plug ins. You can also have your vehicle hardwired with a power inverter to run a vest. We've hooked one to the batter of our car (not hardwired) and had ds vest in the parking lot of a campground when he went camping with daycare. Short notice, so we haven't had it professionally/permantly installed. Needs to be hardwired though, if you try plugging in a vest with a cigarette lighter or plugins that come with new cars, you're going to blow a fuse. Couple friends have tried this on trips to the City for CF appointments. Noexcuses blog has some hints, info on vesting/nebbing on the fly. Think she used an E-Flow, which was acceptable for tobi and pulmozyme.