This may be a stupid idea. I don't know as I've never tried it. You could look for an old lugged road bike at a garage sale that has 27 inch tires. Then you could swap the 700 rims and such over from your road bike (assuming that they're strong enough for cross). You could also swap your shifters and derailers over to the 27 inch frame. The reasoning behind this is that with the added tire clearance you could throw some cross knobbies on there and be in business. Although it would take some knowledge, finesse and maybe even some duct tape I'm betting it's possible.

I say again: I have not ever done this. It's just an idea. I also do not recomend this if you do not know how to put your road bike back together again properly.