Alternative to what? Which foods? Held how long? What kind of transportation do you have? Does the name Cres-Cor ring a bell? Are Cambros out of your price range?
Your best bet might be the new food "cooler" bag from KFC. Pick up a bucket today and get a free bag.
Seriously though ... the picnic cooler bag is the right idea. I used it as a snarky way of saying, you can use regular foam and plastic coolers -- for some foods, like roast meats, you can make a virtue out of necessity and allow a prolonged and worthwhile "resting" time.
Again, depending on which foods and how long held: You might want to warm the cooler first, by sloshing a little boiling water around; and once the cooler is loaded, by packing any unused space with wadded up newspaper and towels, and by keeping the coolers tightly closed with bungees or duct tape; and if the weather is truly inclement, by insulating the coolers themselves in blankets.
Coolers are SOP with caterers who haven't graduated into the equipment big leagues.