There is a mighty hoop that I like for full backs that are great even for carhart. I did a lot of horse blankets and it works for those as well. It's a 438x421 (that's not accounting for pressure feet etc, so actual size is smaller).
I haven't gotten supplies/hoops from Amazon, so that definitely could be a whole different situation with what is or isn't marked. Doing a quick search, some of those are brands that I have never heard of. Some of that could be, because it may be for the home market, I dunno.