I would definitely try the fashion district if you're nearby and see if you can't stumble across a roll of something promising that you could get down to a good price. The closest online products are Distinctive Fabrics' extra long pile (which you saw), and CRs Crafts sells a "palomino fox" that has a 2 1/4" pile. That same fur is also available in white. It's manufactured by Monterey Mills, and you can buy in (serious) bulk from them, though I'm pretty sure for custom runs you have to buy 300 yds. Don't know what other colors of that long fur are available, and it's not all that soft. There are other manufacturers of really high-quality faux fur meant to mimic the real thing, but it's $50/yd and up and very long pile is still rare...
Another option--and perhaps I should say "option" because it's absolutely not feasible for your purposes unless you have a solid gold kidney to sell--is National Fiber Technologies. They make stuff for movies, and they actually carry faux yak fur. It's $40 per square foot. :D
You could always do most of the suit in a shorter (less expensive) fur--even a super cheap fun fur (<$15/yd) and then do neck, belly, or feet fluff in the fancy stuff.