How far to one side of the centerline of the toilet is it? (I know you said "directly behind", but is it at least a little to one side or the other?)
Regardless, if you're up to a little plumbing, you could just 90 over a couple of inches, or possibly even do something like an angle stop right where it comes out of the wall. I would think that there would be room behind the Ultramax II for that if you have a full 12" rough-in, but you can measure off of the ones you have, I'm sure. Give us a little more info and we may have more suggestions.