Has anyone seen toff recently? He had what looked like a radar surface map of Venus for his Venus Transit Map, but I don't recall if he said where it came from.

If that false color image is of sufficient resolution, you might be able to remap the colors to a more usable grayscale heightmap. As I recall, there's a topo made from Magellan data that uses a rather garish hypsometric scheme. If that's the one you have, then the reds are high altitude, the blues are low altitude, and the grays are areas where no data was captured. I considered using that image to get a displacement map for a 3d model of the planet, but I never had cause to look beneath the clouds, so it's sitting in one of my archives somewhere. I seem to remember that it was quite low-res, though, so I'd have had to do some pretty serious processing on it to get a usable texture, anyway.