I did some research on this a while back. http://www.worldofpowersports.com/ for OEM part numbers, and the GSF400 Bandits had the same front wheel (3.00x17) If you peek behind that gray thing where the speedo gearbox is, there is a bolt pattern for another rotor. The GSF400 uses this, so I imagine GSF400 caliper and lines (ebay), rotor.

The other (hard?) issues are:

connecting the hydraulics with a longer banjo bolt to connect the right-side caliper to the bandit distribution thingy
machining and welding a pair of tabs to mount the caliper to the left fork.

Wouldn't have to change the front end at all!

Granted these are not high-performance 6-piston calipers for stoppies, but I imagine there would be some improvement. GSF400 brake stuff can probably be had for 100 bucks, and some money spent at a machine shop for the tabs, and you have twin front brakes.

any thoughts?

Ummmm.  or you could get a katana front end for 200-250 and not have to worry about figuring out where to weld tabs and if the weld job is worth half a shaZam!.  I think this subject has been touched on before and it's been concluded that just replacing is the better option

I searched the forums (apparently not well enough) and didn't see anything on this.

I guess if you're willing to take the risk on the welds its a decent and cheap idea, otherwise meh. Thanks!

F1 CBR forks slip into the GS500 tripples.  You run the CBR wheel and brakes.  It's cheap and you get twin rotors.  100% pointless, though.  The last thing the GS needs is a heavier front wheel.

My Gix front felt slightly heavier and it was well worth it

Yeah, I tried it out and the CBR swap works just fine. Night and day differnce in the shock quality, the brakes are only a little bit better though. I'll sell it to ya cheap, PM me