Off to trusty eBay with no results. So I got the dimensions (6 x 14 x 5mm) and went searching further to discover VXB Bearing selling through Amazon.
They might actually be delivered in two days!
Luckily the clutch release bearing can be removed easily without dismantling the bike. Pulling it out revealed that there's nothing really wrong with it, except some radial wear inside the bearing holder cup. Since there really isn't supposed to be any radial load, and I can probably attribute that to some numbskull in the past putting a frapping nail in place of the clutch push rod.
The release bearing is easily removed. Notice my clever Viton o-ring seal "glued" to the outside lip of the gearbox.
The locknut is knocked loose, then removed, after that the bolt can be removed.
The balls look fine. There's a little wear on the races, but nowhere near anything catastrophic. With nothing to keep the balls evenly spaced, I'm sure they're bumping into one another, shifting the load on the races.
The whole assembly fits together like this and then drops down into the cup.
Sorry for the blurry picture, but the wear inside the cup is evident from some radial load on the bearing.
The next installment will be investigating the installation of the new bearing.