Option 1: watch CL for a used bike. Cross bikes come up every now and then, but not often.
Option 2: Log on to BikesDirect.com and buy a new one for really cheap and bring it to me to build up and fit for free. It's good stuff and way cheaper than a shop. Not what the cool kids are riding, but F the Euro-cross Snobbies!
Option 3: If i were going to race cross again I would take my old rigid mtn/commuter bike, strip it down and put some super skinny mtn tires on it. When I was racing, half of the really fast guys were doing this with their old mtn bikes. The EuroSnobbies hated it.
Option 4: (best option imho, primarely because it the cheapest) Find a really old road bike. Needs to have center-pull brakes and 700c wheels. Stuff some cross tires on it. Get some reeaallly wide road bars and maybe an old bar end shifter for the rear gears. Strip the front down to a single chainring. This is authentic Cross COOL.
Rarely ride the bike and instead train by running wind sprints on the steepest dirt hill you can find for 45min. straight. (puking from exertion should be a common occurrence) sign up for the next cross race and kick the shit out of every eurosnobbie in your class
. Later, on the podium, make sure to give all the credit to your mechanic. (that would be me
)