Yup, Phil Wood is probably your ultimate source. They supply bearings, spindles to fit em, and of course the quality is top notch, and the cost reflects it. Precise, bombproof stuff.
Otherwise, you can look for my secret weapon of choice, Mavics conical-ringed BB. That sucker is the smoothest, best sealed, longest lasting BB in the world, and requires no threading whatsoever in the BB shell. In wi, where the weathers always wet, muddy, and miserable, and the hills are steep & many, those units have held up better than anyone elses BBs for over a decade, in every instance out of the shop. The fact that they'll fit any frame is an added bonus. They show up on ebay from time to time.
If you're going to keep using your microdrive setup & microdrive was based on a 50mm chianline, using a spindle width of 108 will drop 10mm off each side, and pull your rings back where they need to be. While you've still got your 128mm in there, make sure you have enough clearance between your cranks & your chainstays to afford taking 10mm out (per side) without clanking fresh exciting holes through your frame.
Can someone verify that Suntour MD was 50mm? My old MD kit is all packed up in a box back in Colorado.