When I bought my cx4 storm (2 years ago), I looked into the 45acp model. I, at that time, could not find any high capacity magazines. I went with the 9mm instead (30 rounders easy to find). I hope u have better luck than me. I think the 45 storm is pretty cool.
I had the 40S&W and went through the same kind of search as you. Unfortunately during my search I did read up a lot of the 45 acp model. It seems that the lack of a higher capacity magazine was one of the reasons why the 40 and 45 models were not so hot of a seller.