You might want to think about repurposing livestock troughs or bunk feeders -- they're all the rage these days among backyard gardeners. My local Tractor Supply has bunk feeders in all sorts of lengths.
Or you could use metal water troughs up on some sort of sturdy platform -- maybe made of heavy metal pipes -- at a comfortable height for you. These also come in a wide variety of lengths and depths.
I like the trough on a platform idea!
I remember watching a video about a couple who had a homestead in the Cochise County, Arizona desert.
I wish I could find it. They had all their raised beds on platforms not just because of bad soil and aging backs but to keep varmints out.