Heres another option.

http://www.dawesdevices.com/boost.html

Or you can also build one yourself for less than $10.

http://pages.cthome.net/gus/mike.html

Or here is the best looking manual controller around

http://www.turboxs.com/

Ive used a couple of the home made ones as well as the Turbo XS. Thy all work equally well but the TurboXS is easiest to adjust and looks better.

Just make sure you dont use a bleed. Make sure its a ball and spring. The bleeds spool the turbo too slowly.