Any .fx file should work with XSI, even doylle's 3dsMax Viewport Shader below.
Index of /images/temp/XSI/shaders
There are two quick ones I quickly created with Mental Mill (it's very easy to create realtime shaders with, and is node-based similar to XSI and the Unreal Engine's Material Editor), and there's bound to be plenty of better .fx shaders floating around that actually had some care and time put into.
Be sure to open the shader's properties and adjust the light around, lower their intensity, etc.