Re:
RockShox has always accommodated Klein frames beginning with the Mag 20/21 and the MC1 frames. Basically while the rest of the world was using a RockShox fork with 1 1/8" steerer tubes out of the box, RockShox had to modify their fork with a 1 ¼" steerer to accommodate the larger head tubes of the Klein frames. The only difference between a Mag 21 or Judy SL that fits a "normal" bike and one that fits a Klein is the steerer tube. So...if you have a fork you want to use with your Klein, without using any head tube reducer kits, you just have to make sure the steerer tube is 1 ¼" in diameter. For a RockShox fork, you can look for a steerer tube/crown itself which regularly come up on eBay or here, or you can buy a whole fork and swap the stanchions and lower parts of a RockShox fork you already have onto the larger, Klein-compatible 1 ¼" steerer/crown. I'm not as familiar with White Brothers forks but I can't recall a Klein that was fitted with one. Probably not impossible but you'll either have to find a larger diameter steerer/crown or, as was already suggested, use a headset reducer kit that modifies the Klein head tube from 1 1/14" to 1 1/8". Hope this helps. Let me know if you're still interested in the MC2 and I'll forward you pics (it's in perfect condition - no scratches, scuffs, etc and hasn't been cut down).