My Iphone 4 lock button broke?

My Iphone lock button just suddenly stopped working. It is very annoying to not have it working. I have been reading these a lot and have come to the conclusion that I cannot pay to just have the button replaced. -It is out of warranty
I read that it is like 150 or 200 to replace the phone. I was wondering if it was possible to trade up to the iphone 4s and if I could choose between black and white. like switch my colour? and how much that would cost. I was just wondering because if I have to pay and get a new phone I don't want to pay to get something that is the same and identicle. I would like to have something that at least seems kind of exciting for the amount of money I have to spend on it.
I was hoping that this phone would have lasted till my contract was over and I could sign with bell again for the iphone 5 but it seems that my stuid button had to break and force me to by a new phone before that:(

Thanks