I just bought a couple of these 'big fermenting buckets' from Home Depot. They are the Rubbermaid 'Brute' 'trash cans'. They are food grade and are used alot in the food industry. The white, green and gray are all food grade. It will give you the classification and number on the bottom of the container.
Here is from their website:" Seamless, polyethylene construction won't dent, rust or leak. Reinforced rim and base. All colors are NSF/USDA Approved for food contact and NSF tested/certified"
I paid$29.97 each. The 'wheeled carts' also are the same price but I bought a 1/2 size furniture dolly from Harbor Freight for $9 and works just fine.
Don't "waste" your money on the rollers for the Brute. I got one last year and "refuse" to use it. When you get the can half full of grapes it becomes very top heavy and will spill over if you look at it wrong. The device is just plain "garbage".Put the Brute where you want it and leave it there when full. I have ten of them I use. Sorry for that, but the rollers just plain "stink"!
I missed that part of the post- I full up to under the top wide ring about 6-8 inches down for primary fermentation. I keep it down about 4-5 inches for the whites and that is plenty. The reds at 6-8 inches doen will hit the lid withing a few hours. I have never had one bubble over at that level.