yes you can replace the original plate holder. It doesn't need to be approved by the tüv (in Europe), so you can just make your own or install an aftermarket one. however to be legal it needs to be at a 30° angle (again this is European law, not sure about Canada/US). I have made my own with some aluminum strips, cheap and easy. Mine isn't set at 30° but closer to 40°, but when I was at the regular tüv check last year he said it was ok, because if it were at 30° it would risk getting ripped off by the wheel. As long as it can be seen properly from behind it's fine. Plus since it's flexible aluminum I can just bend it over more if a cop complains.
The brake light is a different issues, here anyway. you are not allowed to install lights that don't have the tüv logo on it. so when buying aftermarket that's something you need to look out for, to make sure it's approved.