This should work to get rid of the password prompt.
copy scp://cmalott21:PASSWORD@192.168.1.1/<IOS> flash:<IOS>
Just as an FYI - I just did this a bit ago on a couple hundred routers and noticed a few things. First, FTP is the fastest protocol to upgrade with that I could find. SCP was actually one of the slowest, pretty close to TFTP. However, caveat on that, don't use Microsoft's FTP server, it times out trying to start things up and screws with whatever type of script you try and use without a ton of fudging. I got it working, but moved to FileZilla FTP server and got things working much faster and smoother.
Once I got things running smoother, whether I did it via a config change template or a simple script didn't matter too much...