Phasers and flangers both do swirly sounds, but they are completely different in how they work. Flangers are a modulated-delay effect, with more in common to a chorus than a phaser.
You can some times fake a phaser sound by keeping the flanger's resonance low and messing with the delay time and depth, but IMO it's not very convincing. Another solution would be a digital multi-modulation pedal, which contains models of various different types of effects.
If you want "real" effects instead of digital models, a pair of Mooer mini-pedals would do the trick. I've heard their Phase 90 clone is pretty good, and I know they have a flanger as well.