Three options are available:

1) An adjustable stem that will let you raise the bars by varying the angle but that, of course, changes the reach too.

2) Using a quill stem adapter ( Nashbar Stem Adaptor ) will let you use a threadless stem and these are available in a wider variety of angles and reaches, including adjustable ( Nashbar Adjustable Stem ) so you should be able to find a combination that works.

3) A long quill stem like the Nitto Technomic ( Nitto Tallux Stem ). The Nitto isn't particularly cheap but it is a high quality stem and seems to be just what you want.