Another CN member mentioned a site which was selling old University Optics 2" right-angled prism diagonals (1980's/'90s vintage) for $150.
Link to vendor selling older UO 2" prism.
Scroll down to "STAR DIAGONALS,2"/1.25"/.965",VISUAL BACKS,ADAPTERS,FOCUSERS".
It's in that grouping.

That's probably the least expensive 2" star diagonal prism around these days.