This appears closest to what I'm after - but this looks like it uses a 2D rendered isometric board:
www.ufo-extraterrestrials.com/UFO_ET_Searching.html
www.ufo-extraterrestrials.com/UFO_ET_Searching.html
You have a better eye than me. Before I played it, I thought it was 3d, but now that I've played it, you're right, it's using a 2d renderered isometric map.