Perfect, this is what I was looking for!
I can't find it anymore but there was a link, perhaps it was Huaqizhengbang's website, where they had the usual 3040 and also bigger models (perhaps one was the 6040). Searching those part numbers didn't turn up any for sale, unfortunately. But maybe that's because its simple enough to add longer bars or a whole plate like you are doing.
Good looking out on Charmhigh. I wasn't going to buy from them but its good to know!