You're right, there are several different options here, but once you see pics, it shouldn't be too complicated. The new-gen 250 (and the 300, and the 400), can use "normal" front stands and rear stands just fine from a company like Pit-Bull. You need to get spools to screw into the threaded holes on the side of your swingarm for the rear stand to lift, anywhere you buy the stand will likely offer the spools as well (they are just a couple of bucks). On the front stand, for the type that lifts from under the triple-tree, you need to get a pin that fits the ninjette. Again, anywhere you buy the front stand from can check to make sure they are getting you the correct size pin. Going forward, you can use these stands on pretty much any bike you get, just by getting the right size pin for the front stand, and making sure the bike has rear spools. You can get away without the spools by using a rear stand that just lifts the swingarm from underneath, but you really don't want to do that - the spools give it much more stability.
There are also more unique looking stands that hold the whole bike up with just one strong piece in the center of the bike, by mounting to an adapter that you attach to your frame. These typically let you wheel the bike around the garage, and easily give access to the front and rear wheel while lifted. They are generally more expensive than simple front/rear stands.
PitBull stands have been the "standard" for many years, so much so that if you looked locally on craigslist, facebook marketplace, or another local board, you might even find some used ones up for sale. There are cheaper options out there, some of them quite good, others not so much. I have no experience with those other than the Pitbulls, but others have shared some on this board.
https://www.ninjette.org/forums/showthread.php?t=9810
https://www.ninjette.org/forums/showthread.php?t=45898
https://www.ninjette.org/forums/showthread.php?t=238806