Radian gauges are difficult to find and when available, the red on the face tends to be faded out.
Yamaha made several other bikes that had speedometers which will bolt into the Radian cluster and that are more readily available. Here's what I've found (note that the max speed shown on the speedometer varies depending on the bike):
YX600 (Radian) gauges:
XV535 (Virago 535) Speedometer:
XV1100 (Virago 1100) Speedometer:
VMX1200 (V-Max 1200) Speedometer:
FZX700 (Fazer) Speedometer:
I actually really like the looks of the XV535 speedometer as the blue is very similar to the XJ600N gauges and I don't think it'd look bad being missmatched from the tach.
Because these bikes all share different size front wheels from the XJ600, there will be some error shown on the speedometer. Here's my estimation on the accuracy of these different speedos. The Radian and Fazer speedometers are the closest to the stock XJ600 speedometer:
So that's it; depending on what you're looking for, and if you have the Radian cluster already, here are some options for speedometer replacements that might have better faces.