Is there a way to legally download DLC to a PC and transfer it to Xbox?

Here is my current situation:

1. I am currently in Afghanistan and will be here until next spring.

2. I have access to Xbox Live using an AT&T MiFi 2372 and an Afghanistan sim card.

3. I could download it directly but the connection is SLOW (on a good day I might get two times the speed of dial-up) and it constantly disconnects, meaning I have to constantly watch the screen to verify it didn't sign out of Live and reconnect manually if it does.

It took me three days to download one map pack for MW3 due to constantly having to reconnect. Also, I have a 2GB a month limit and unlike in the US where you just get overage charges over here when you hit your limit the connection just shuts off until you load more credits.

There is an area on our base with a 2meg download wireless connection I could use for free, but for practical reasons I can't bring my Xbox directly there to do it. I could bring my phone and download stuff to it directly or I can take my laptop.

Any suggestions? Once again, I am not asking how to download pirated DLC, I'm asking if it can be legally obtained on a PC after paying for it.