http://partzilla.com/parts/detail/aftermarket/xp-4135468.html
it is a vm44 mikuni   looks like a good option to me, anybody try this out yet?
the price seems good at $120

The round slide VM44 is a good carb for high end power once it's set up right and kinda sluggish on the low-mid range.
Price is cheap, but it's also not a bolt and go carb, something about the throttle cable not fully raising the slide, I don't remember.
On the old site there were a few guys running the VM44's.

I just installed a vm44 that has the DrQ mods. Its now a 46.5 I think... Anyway I couldn't be happier with the performance gain and I'm not going lean on a long pull anymore. DrQ quizzed me on my riding style and porting and modified the carb accordingly. I used a throttle cable that has a 60 degree bend at the end and it fits right up next to the frame tube.  I also used a moose thumb throttle which is good for 50+ mm slide. (Q said a stock would also work if I did a small alteration on the OEM thumb throttle.)  The carb swings right over for needle and pilot access and the main is easy to access. Q helped me with the jetting on Saturday over the phone. All in all a great experience.