I'm pretty sure it's out.  I could have sworn I've seen it on scion.com just a day or two ago, but I can't seem to find it now.  Here's a link to my local dealer's website for accessory pricing.  The 18th item on the list says TRD Quick Shifter for the xB.  Unless stated otherwise, all accessories on that page are supposed to be for the '08 models.  I did a google search and found a couple other dealer websites offering the same item, but can't find it in the TRD catalog, on eBay, newscionparts.com, or TRDsparks.com.  I'll ask my dealer today if I get the chance.

http://www.newarkscionworld.com/Scion-Accessories.aspx

I doubt it's the same one if they can't be found on those sites or eBay.

This might be the part #: PTR03-52083 
Prices may range from $150 to $249 installed.

I may make that one of my first mods. I always wanted to do it in my Jetta but never did. My Jetta actualy had two different ones avaliable. Both gave a 10% shorter throw and could be used together for a total of 20% decrease.

I did some web surfing and have come to the conclusion that PTR03-52083 and PTR46-52080 are both quickshifters for the xB2.  However, both are TRD and for whatever reason the first of the two is only $229 w/install and the latter is $335 and there are much fewer places to find it.  Next time I place a part order at my Scion dealer, I'll ask them to run the two numbers to see whats diff.