My wife's Terry runs a 24 on the front and it is a REAL challenge to match a 24 front and a 27 rear and had me looking.
Niagara has about the best selections of 24's.
http://www.niagaracycle.com/index.php?cPath=131_165

They are a discounter and most of the stuff you see on their page is what htey were able to get a smoking deal on. If you don't see what you are looking for call. I am pretty sure they can get the Pasella in that size.