Finally a cheaper DVI- SDI converter

http://www.gefen.com/kvm/product.jsp?prod_id=2566

works both way, dvi to sdi and hd-sdi and sdi to dvi...

Configuration for a DVI to SDI conversion requires no more than a simple selection on the unit.
Addendum:

As of March 2005 ( i emailed their tech support )- gefen is no longer supporting dvi-sdi conversion.