Download m4a file to iphone from windows machine

I have a laptop (Windows 7 if it matters) which isn't one of my main machines. Well, I was doing stuff in the garage and figured I could use this laptop out here, with some old speakers, and pump some music into the garage while I did some work. I know that my more recent iTunes purchases are not protected in the M4P format, but can be downloaded as an M4A and copied over to another computer (not on the cloud, but physically transferred and added to the library). But even those M4A files can't be accessed.

So that got me to thinking -- some of my newer purchases *are* M4A (unprotected) files when downloading from an authorized computer. But I can't access them or download them on this laptop because it isn't "authorized". The problem is, I don't want to use up one of my five authorizations on this computer; if that means I can't access the earlier purchased content in M4P format, that's fine. But is there a way I can access the purchased, unprotected M4A files other than going to an authorized computer and physically downloading them all and transferring them? I can do it with that brute force method if need be, but I'm curious if there is another way.