Does anyone make ready-made small water guzzlers, like would fit on a trailer?

W-W
LFM Bul Tuf

Try here

https://plateauwildlife.com/wp-content/uploads/2017/12/Plateau-Water-Table-100-1.pdf

Not a guzzler but you could make a roof that would fill it easily.
https://banksoutdoors.com/product-category/watering-systems/

On Craigslist in Austin Area a guy was selling them. Basically a square plastic tank on a steel stand with a metal roof to fill the water container and a spigot on the end. Look up Cisterns, deeer blinds, etc. I believe they made deer blinds and feeders as well.

Thanks to all. I inherited a few square plastic lick-tubs on the new place and I've been thinking about using them as catchment ponds, so to speak, each piped downhill to some sort of water manifold, then further downhill into a holding tank, then further downhill to a small trough. 'Just have to find the right location on the place.