They make extenders but not really for mtn bike use and I'm not sure it would work here anyhow. I've seen people fabircate their own but not sure I'd trust it. Best bet is to bite the bullet, sell it and purchase the correct fork. Chalk it up as lesson learned.
^ He could get a another frame that fits the fork
Why not?and no, new frame doesn't count.
Why not?
You're right... new bike > new frameit is a perfectly good idea, if it is a step towards getting a NEW BIKE!