In reply to weston.front:
I used Poste Restante in Norway last summer, I ordered from within EU to try and avoid as much customs problems as possible but it still got stuck with me needing to register for a customs ID number. It didn't cost anything but delayed my journey by a couple days. In future I'm going to order from within Norway to avoid any issues as have done in the past without problem.
The route looks like it goes through Leknes about half way which has a good selection of shops including an outdoor shop. So posting food in advance shouldn't be necessary.
https://www.toll.no/en/corporate/import/how-to-apply-for-a-trk---customs-id...