The Greek government's problem is that it doesn't have enough euros. It also doesn't have the power to simply print more.
It doesn't?
I've seen several claims that Greece (the central bank, as opposed to the government) has a €uro printing press.
Indeed, wikipedia says there's a 'Y' prefix for the banknote serial numbers printed in Greece.
So, what's to stop them just running this press until it melts? Using the local plod/squaddies to commandeer it and whisk it off to a Natanz-style fortress if necessary.
Just for lulz, they could print them with 'X' prefixes instead of 'Y'.