You can make them easily enough yourself, one popular method is to use the Unpowered plastic cement mixer drum that used to be available online.
Its a drum with a lid and two agitator bars affixed inside. put in clothes, detergent, hot water, screw on the lid and roll it around the floor for a few minutes. I've seen folks modify them into being fitted into a cradle so you can spin it with a handle. takes up to 10 lb load.
Think I will have a go making one ....winter project no 1 .....looks easy enough.
if anyone can make you its you SS !!
sorry,typo error, that should read, if anyone can make one, its you SS !!