The linked louver says it's for 2 different fan models - so it may not interface with the standard ducting sizes for residential fans, something to keep in mind or see if there's a PDF out there somewhere.
There's plenty of ways to go light-tight though, even using flex tubing sprayed black inside and curled around once... or make a black plywood box with in and out on the same side. Honestly, go into a residential bathroom, turn off the lights, and see if anything makes it into the fan photon-wise - I've never seen it, probably in most cases the path the ducting takes ends up blocking the light.
The bigger issue is where does the exhaust actually go? You could just blow it into a well-ventilated attic I suppose, if there's no inspection and permitting going on. Even straight selenium would probably dissipate enough not to worry (yes, flame away on that one folks, and I wouldn't personally do that, who knows how that stuff interacts with insulation, etc.) Getting a proper vent cap installed (so that rain doesn't damage your roof over time) is a DIY job if your roof is DIY friendly. (Mine's about 30 feet up and steep, I freaking hate it up there!!! When we had our roof redone I bought three vent caps and had them installed for future remodeling).
You can also install a wall-mounted vent, that can be much easier. On a brick house, you need to get a hole through the brick (multiple small holes with a masonry drill around the circumference you need, and then smack with a hammer, clean up with a chisel), and you need tapcons to hold the cap to the wall, caulk, and screen - birds love building nests in those things!
If you live in a hot climate and run the AC all summer, humidity can condense on vent piping (which will be cold like a beer bottle) and you can get some serious staining on your ceiling as it drips and pools. You need to wrap exhaust piping/tubing in duct insulation, or spray solid ducting with spray foam.
And when you attach ducting, flex tubing, etc... don't use duct tape!!! It's really not for ducts. Use the silver-foil style HVAC tape (any hardware or big box has it), and also use zip ties to attach flex tubing to solid tubing and mounting flanges (after you tape). Duct tape dries out in a year or so and falls apart, the silver foil is decades-good. Pain in the rear to get the backing off, then you're solid.