the bearings are Klein specific, not standard at all. they might be still available through your friendly Klein/Trek dealer. part no. 971604 2.0" outer diameter. they are the same top and bottom on the MC1 frames.
most important is that the bearing seats in the frame and on the fork are perfectly clean and that there are no scratches etc. otherwise the bearings will get stuck. put the bearings and ideally also the fork into the fridge for a while so that they shrink. take them out, wipe them dry, apply the Loctite and carefully put them into the frame. heating up the frame with a hair dryer helps too. don't forget to mount the bottom seal and then apply some Locite on the bearing seat of the fork and push it in. if everything is perfectly clean it does not need too much force to mount the fork.
alternatively you can mount the seal and the lower bearing on the fork and then press fork and bearing into the frame.