A good manual washer is the Wonder Washer. I had one. Used a wringer I got from a fellow junker. Downside is you have to hang all the clothes on a line to dry. A lot of campgrounds won't let you do that. And I had the gift of making it rain every time I did laundry. It's why I started hanging the clothes under the awning to dry. In NM, I would hang the wet clothes up and the wind would start up and I would have to rewash them since they were muddy. Ended up using a laundromat in NM. When we laid out the bus, we planned for a topload washer & dryer. Just waited until the time was right then bought used.
If you decide to go the Wonder Washer route, let me know and I will give you a link to the directions and load sizes I have posted.