Sure, it's fairly cheap and easy to make yourself a Portal-themed mirror with some paint and a quick trip to IKEA. But what really makes a portal fun isn't just its blue or orange halo but rather, that trippy infinity effect.
For that, you need two mirrors. And some LEDs. Or if you're not particularly good with putting things together, you just need this Etsy seller to do it for you.
The downside is, they're not nearly as effective in the broad daylight. But at night, or in a darkened room? Not going to lie: it's kind of tempting to try to leap through them.
Portal Mirrors [Etsy]