These things are commonly available on Ebay, new.
There is also a new version of this, sold by a guy in Canada, that does have a drain hose, and I think also a hose for filling, that you can attach to the sink. So you put the machine at the edge of the sink, and you can fill & drain without having to lift a heavy 5-gallon bucket full of water.
There are a couple of other versions of these that have fill & drain hoses, one of which is rectangular and transparent colored plastic. I suspect that the version w/o the hoses will eventually be phased out.
Capacity of most of these is about 2 lbs of laundry, which is to say, one pair of jeans or two outer shirts or a few undershirts or pairs of underpants. I could see them being useful for when you're on the road, or when you just need to wash a couple of items (e.g. "I need this shirt to wear to the meeting tomorrow...").
laundryalternative.com sells a matching countertop spinner for $70 which is rated at 2 lbs. capacity. This will relieve you of the hassle of wringing out the clothes washed in the countertop washers above. It also has transparent sides, so you can watch the water spin out and stop the machine when it's done.