Velocity took up the 650B cause early on and still makes the best rims we've seen. The Synergy model is ideally suited to carrying tires between 28mm and 45mm.

It's 22.68mm (or so) wide, good for holding tires 32mm and wider; and has a tall (11.21mm or so) braking surface for easy brake set-up. It has eyelets, and is available in  front (symmetrical) and rear (asymmetrical) versions, in either 32 or 36 hole.

It may be some time before other rim makers see a market for 650B rims, but it hardly matters...because they won't out-do this one. This is the rim we use on about 80 percent of the bikes we assemble. (If you include the 26-inch and 700C versions).
Silver only.

$20 shipping for rims, up to 6. $30 for 7 or more.