Ignored Requests Open-Source Software from a Research Group
I think contacting the editor of the journal is your best bet. Contacting grant agencies will most likely not warrant a reply, and I don't imagine many of them have stipulations for sharing code (yet). 

That said, I have been in a similar position numerous times, and I have had very little luck every obtaining the code. The editor will most likely not be willing to retract a paper because the author's won't share, and they have little incentive to do so, since it will at most garner a single citation, but could lead to more problems down the road (e.g., the code is buggy and you can't reproduce their results, etc.)

Another tip would be that senior people (i.e., PIs) usually have more luck at this kind of thing because they are harder to ignore and/or have contacts, but it can be harder to get the to actually do it, because it can become political.