One other thing.. you could convert to a threadless stem attachment, like this:

DIMENSION QUILL STEM ADAPTOR at JensonUSA.com

That would let you attach any number of different risers, since they are readily available for the threadless style of steer tube:
One of these for example:
Stem Raiser, 1-1/8 Threadless - black

Then you attach a new stem to secure your handlebars:
Alloy Hi-Rise stem, (25.4) 45d x 80mm silver

You could have those bars way up in the air if you wanted.