Fiio E5 being the cheapest one in production, and maybe the Ray Sammuel Audio P51 Mustang being on the other end of the spectrum. There's also Xin Amps, however he's been known to be a very unreliable character.
If you can wait, Pico Slim and RSA Shadow look to be highly promising.
For the pico I would expect it to be in the same range as the original judging up the shadow it may be a bit less then a p-51 or 71a was but I am certain that it won't be a bang for the buck type deal. I would not be surprised if the shadow was marketed around the same price as the tomahawk was. Again purely speculation as absolutely no details have been release yet.