Are there any mirrors in space? We have encountered galaxies that act as lenses, magnifying the light coming from behind them. This is super fascinating and it makes me wonder what other optic tools we might have at our disposal.

The question of what we know about our own galaxy is obviously fascinating because it's kind of the the one we have the worst view at. There's so much noise around us it's hard to get a macroscopic view of the galaxy. It occurs to me that if we could stick a mirror out and look at our galaxy from the outside, maybe we have a better view. 

Of course, we don't have the technology to make a very useful mirror. And it wouldn't be very efficient. If anything, we would simply launch a probe out there and send back pictures and science data.

But then I got to thinking maybe there's a naturally occurring mirror we could leverage. We know there are entities that can bend light, are there any that bounce it? It would be incredibly advantageous if there was one that allowed us to see our own galaxy, but also it seems unlikely. But are there -any- objects out there that reflect light like a mirror allowing us to see around them or behind them or their "backside"?
Very likely not.

If it's a gravitational process like galaxy lensing, then a "mirror" would require a very large deviation. That's extremely unlikely with this process.

With other processes, e.g. classic reflection, it seems even more unlikely. We don't know any natural processes that could craft mirrors at cosmic scale.