I have a clay, but don't smoke it very often. It is just too small. I tried to find a maker that produced larger clay pipes a couple years ago, and thought I had found one out of England, but when contacted, I was informed that they no longer produced clay pipes, and didn't think they would do so again any time soon.
I think that it wouldn't be too difficult for some manufacturer that already makes them, to create a mold of a more hand filling size, with maybe thicker walls. I'm sure they would sell. But so far, I don't think anyone one has. At least from what I see available.