Does anyone know where to get Large Clear vinyl transfer sheets for large piece of fondant, like on the food challenges? I checked Home Depot but didn't see anything.

fabric stores.

if your Walmart still has a fabric dept (most don't any more) then they have it too.

it's the vinyl made for covering tables to protect the table cloth

Joann's has it - upholstery vinyl....you can get it in several different guages.