Dingwall do indeed make a J-type, though it costs at least £3k new and ~£2k used. Sandberg make J-types but they’re almost all active (in an ideal world I’d prefer passive) and, sadly, I’m not a fan of the new body shapes. MTD USA falls into a similar boat to my Dingwall argument re: price and MTD Kingston do make J-types (known as the Saratoga) which I’ve considered and not ruled out despite being active, because the Saratoga preamp is arguably even more convenient than the Yamaha preamp.
Still, would you complain if Yamaha made a J??