Wanted: Campagnolo seat binder bolt

another binder question:

Do binders come at a standard length, or are they easily bought at varying lengths?
I need one a little longer than the one I have now. Evans recommended I buy a new seat post seeing as my binder doesn't fit: hoping there's another option...

What?! Bad plan if that reads how I think it reads..! Fitting a thinner seatpost is not a good idea :-)