You can get the tapered bearings directly from the BBR site... Not exactly sure, but I think they run around $39.99 or close.
Originally, I had installed my BBR fork with the stock bearings. The only real trouble I had was tightening the slotted collar nut located directly underneath the top triple clamp. There seems to be a very fine line between tightening that nut too tight or too loose. Because, when you tighten down the nut atop of the triple clamp, it would somewhat tighten the slotted collar nut at the same time thus resulting in the bearings being too tightly torqued.
My fix was to install the BBR tapered bearing kit. I punched out the stock bearing races and tapped in the new ones. Then I tapped down the lower bearing onto the steer tube of the fork using some PVC pipe as a slide hammer of sorts. Then, just simply slide the steer tube into the head tube and slide on the top bearing. I then installed the plastic cup/seal over the bearing and threaded on the slotted collar nut until it was snug.
Then install the upper triple clamp over the slotted nut and lastly screw on the top clamp nut and torque down tight.
I found that the bearings did work loose a couple times because I had not fully seated the races, but after those couple times they have remained silky smooth and tight.
I don't think installation was too hard. I'm no expert mechanic and it took me approx 25 minutes I would guess.
Sorry to ramble on... hope this helps you.