Conflict zones like the middle east are hot markets for arms dealers and surplus materiel tend to accumulate there. I doubt there's any direct conduit between the two countries though

identified as North Korean made RPGs

Identified by whom? The same folks that gave us "40 decapitated babies", "they bombed their own hospital", and "we did DNA testing on a random skull fragment to confirm Hamas killed Shani Nicole Louk"?

I think they're able to get supplies into Gaza the same way Hamas gets other supplies in.

The Hamas group has a (likely entirely overstated) tunnel network across borders and a (likely entirely overstated) Mediterranean smuggling operation. That gets you a very limited set of imports from Egypt and perhaps Lebanon, Syria, Cyprus, or Turkey if they can really stretch it without the IDF noticing. None of these countries are doing regular direct trade with a small largely agrarian country on the opposite side of Asia. Nothing from North Korea is getting through the Suez Canal, nevermind it getting packed in across the entire length of Russia. Certainly not a militia's worth of rocket propelled grenades. Come the fuck on.

This shit is almost certainly all home grown. From Egypt or Syria? Very likely. Robbed from the Israelis? Definitely possible. Brought in from Iraq? Sure. Brought in from Iran? Maybe. Brought in from Ukraine? Not outside the bounds of possibility. Brought in from the opposite side of the hemisphere? Give me a fucking break. Might as well claim they're receiving arms from Haiti or Nunavut.