Umm....why would you? The PC is pretty darn portable. I'm sure they have a dutch oven, stock pot or a cooler that you could use.
But, if you really want to, you could use more traditional methods - but you'll be sacrificing the quality of what you've done.
Is all of the meat in the sous vide bags still? If they have a side-by-side sink in their kitchen, you could clamp the PC to the divider in the middle, fill the sink with hot water and use that as a bath to reheat them.
If you hadn't seared them yet, you may be able to get away with the sear bringing them up to temp enough (again, you want a REALLY hot grill...but the core of the thicker cuts will still be quite cool.