Hi,
Not sure if your'e talking about a car GPS or an offroad GPS, but I have a Garmin Etrex 30 and I use the "Topo Canada series". They have all info I find useful, they actually pretty close to the Backroad map books but in a small device.
I dont know if the maps work on all GPS bey they usually work on Garmin brand GPS.
If that whats your looking for, let me know, I have the topo maps for QC, ON, AB an BC and I can send you a copy.
Simon