There generally isn't enough demand to justify middle line bass clarinets. Buffet used to make one, the 1180, I think. Yamaha 221 II is a very good student model I suppose you could consider intermediate. There are some second-tier pro horns that could be considered intermediate, like Malerne, Noblet, Kohlert, etc. Those manufacturers also produced stencils, so you might be able to get a Malerne labeled as a Conn, etc.