40 cu. ft. oxygen tank, regulator, flow valve/meter and a micropore diffuser. Basically the same set-up George1 uses to revive his HSB when he catches them.
Enough non-iodized salt to make a 0.5% solution and a chemical to nutralize ammonia wouldn't hurt either.
Haha, okay, what I really meant was what's the cheapest way I can jury-rig a system that can haul 50 lbs of trout 4 hours on the highway to my place?