If you really want to, don't let anything stop you from doing it. The guy in that video might have had better luck selling his old red ryder since it might have been collectible and modding a new one but what the hell, maybe it was a beater.
Get a length of rail from your favourite supplier, rough up the bottom of the rail and the top of the receiver with 60 grit sandpaper or a metal file and try some epoxy or JB weld. Make sure it's nice and straight as you can get it. I'm sure you could get something working.