Howdy, this is my first post on these forums. Coincidentally, I own the exact Klein Karma MTB that PACERC250T linked up above (The orange and black leaning against the white fence. Bought it just a few months ago via craigslist here in Los Angeles) and have been riding it quite a bit this summer. Great and cushy as a road bike, but as an MTB it'd prolly be lackluster for anyone who isn't a beginner. The rear elastomer suspension is still in good working condition, although my guess is it's more spongy/bouncy than it was when the bike was new.
Since picking up the Karma, I too have been hunting for a backup elastomer just in case the original bites the dust. Unfortunately, my hours of searching came up with zilch. If it'll help get something crafted, I can yank my rear suspension and take measurements/pix or something. Perhaps even find the proper stuff to make a negative mold (w/o damaging the current elastomer) and ship it to the crafter.
Anyhow, here's a couple other pix dug up when I'd been googling. Not of my bike, they're of a Pave model, but looks to be the same as what's on my bike.