I imagine that people like Fidelity or Charles Schwab can offer some stuff. If you're not interested in that, you may want to look at Eurex BTP futures (which I think is offered by IB now) or the various iShares ETFs, although I don't think the latter offer anything periph-specific.
greek debt is an institutional product unless it has been prepackaged for the retail trade which does not seem to be the case.
I know that private banks definitely offer stuff. I can't find a way to do it through an ETF or anything like that. I am sorry I can't be of more help.
If you know of any retail level broker which offers Greek debt I'd be happy to know about that too. Edit: I hadn't read the thread after this post. So like I said in less words, there isn't an ETF or a retail-offered periphery-specific product on the market but if there is one I'd be interested to know where to find it.
Well, I know you're looking for Greece. The closest I can get is Italy, but I am still hunting around.