There's a lot of stuff going on between DH and cyclocross. What kind of fork are you putting on this bike? There's everything from the Banshee Morphine that's built for a 160mm fork (hoirzontal dropouts, can be found ~$400) to a rigid Surly 1x1. I'm not sure if you mentioned the 1x1 because you want a rigid, or because you figured a rigid would be cheaper than a suspended option. And what kid of material are you looking for? Steel? Aluminum? Anything else you'll likely pay a premium for, but you at least have those two options.

If you don't care about old, want something that can take a 100mm fork, and ride a 16" by some chance, Brodie has a closeout '04 1ball on its website for $225.