http://www.niagaracycle.com/categori...-right-7-speed
$13. Just get a new shifter.
If you can find it, yes I just found it in about 3 minutes. Niagra Cycle is GREAT for that! Slow to ship sometimes, but lots of selection!
My 2001 era LX (9spd) started to do the same thing, but removing dust covers and lubing the mechanism worked fine for me. The grease was a bit dry and needed to be removed, which lubing did.