Not having a CMoS camera to play with, I throw this suggestion out for those who do for them to consider.
Take a series of dark exposures under conditions as equal as possible, especially sensor temperature. Fit a smooth curve to the intensity readings at each pixel. Extrapolate back to zero exposure. That is your bias frame.
Rather tedious but I don’t see why it shouldn’t work. Whether bias frames are useful to you I couldn’t say.