What screw did you use to work out it would take 20 secs to travel 900mm ? The 04, 05 and 10 in the version numbers stands for the thread pitch of the screw, so 1 full rotation of the screw would make anything connected to the screw's lead nut move 10mm and so on.

I would find a reduction gearbox first and then go from there, once you've got that sorted out you can then look to a suitable motor. I would probably think about a smaller screw as well, its hard to know what direction to go in as you haven't given us much info on what the intended purpose of the machine is...

Sound like it could be intresting...12v...only 4Nm to move...fit inside a car !?!?!