I use a 5 gallon bucket with a tight fitting lid. About every 180 degrees I have a 2x3 that goes down the inside of the bucket. "I screwed them in place from the outside).
Put the clothes in, add soap and water, put the lid on , place the bucket on it's side and roll it on the ground. I rap a rope around the bucket, then by pulling on one end of the rope at a time I can make it roll away and then toward me. The wood on the inside acts like an agitator.
I was thinking about making a device with 4 wheels facing up so that 2 wheels would be on each side of the bucket. I could spin the bucket while it stays in one place. It could be made small enough to fit into the bucket when not in use. Something like a 8" of 2x3 with a wheel screwed near each end far enough apart to support the bucket on it's side, (times two). Lay the wood on the ground wheels up about a foot apart, then lay the bucket on top of them.