I think continuously make the case that not addressing internal displacement will have a number of knock-on effects that will slow down a country's development trajectory. As well, try to convince these national governments that it is actually in their own self-interest to both prevent and reduce internal displacement risk.
Of course, there will always be sensitivities. There will always be human rights issues that have to be discussed, perhaps separately and in very specific forums, but I think starting the conversation with a development angle and using an economic or financial argument is definitely the way forward.