there are no superchargers made for the Alty. Unless, ofcourse, you go custom. This is very possible and all it takes is, MONEY!!! Lots of it.
F-max does make a turbokit for the 93-97 Altima. I imagine it will fit the 98-99 as well. But, for $4000, just for the kit, i don't think it's worth it. Then again, you could go custom. All you really need is the turbo exhaust manifold. You can get that from f-max and fabricate your own. Route your own piping, get whatever turbo, wastegate, blow off valev, etc, you want. This is more like $1500-$2000
www.racetep.com has a shitload of n/a stuff and forced induction items as well. Check it out.
What i would recommend, the best Bang for the Buck! Nitrous. You can't beat it! The JWT set up is by far the safest way to go. They offer a 65 shot and a 100 shot. No mandatory upgrades. The only one is larger injectors for the 100 shot. Otherwise, a straight 65 horse to the flywheel and an ecu upgrade for around $1500. Check out their website and give them a call for more info.
You could do a search about, but not sure how much stuff will come up.