There's no such beast. A trigger just pulls the vibrations off a drumhead and turns them into an electric pulse that has to be interpreted by a module before it becomes a sound. Nobody to my knowledge has combined the two. The closest would be a multipad controller with a brain, like the Roland SPD-SX or Octopad, or the Yamaha DTX Multi-12. But those are stick-played multipads, not triggers.
Now, triggers are really not that expensive, and you can get a simple module like an Alesis DM5 for between $100-$150. So for less than $200 you can be into a triggered kick setup.
What makes a device that is a drum trigger that generates midi messages directly not viable?
Size, for one. You'd have to build a trigger that includes a MIDI circuit board (pictured). And it would have to be powered. And then it still needs to talk to something. Your MIDI trigger signal has to be sent to a sound module that has a MIDI input. And that sound module, then, has to be hooked up to an amplifier.This really over complicates what could be/is done with a standard drum trigger ..... hooked up to a drum module.