Bokmål and nynorsk are written only. So, you're just looking for Norwegian films.
Norwegian films would of course be the best place to start, but if you're looking for dubbed films, you're going to have to stick with animated films. Subtitles are preferred over dubbing, so there's just not going to be Avengers dubbed in Norwegian. You can find Disney and Pixar films dubbed in Norwegian, however.
Your best bet for actually finding those is to find out what the Norwegian title of the film is, then search for it. DVD's aren't going to work for you unless you can play region 2 DVDs, so that's going to limit you to (legal) downloads.
American films with Norwegian are by and large laughed at, the notable exception being the first few minutes of John Carpenter's The Thing. The new Thing that was released a few years ago has proper Norwegian too.
It's honestly going to be easier to watch Norwegian films with English subtitles. There are plenty out there, although not all are good. It's going to be the best way to hear a variety of dialects, however. You tend to have a lot of recycling of voice actors for kid's shows.