After visiting several local fish stores, I found one that sold Endlers, but they didn't look very pure. They all had different colours and patterns, so they were probably hybrids that had been crossed with guppies. And they were very expensive. So I looked at online ads, and found someone that sold Endlers. I bought 6 male Endlers from him, 5 adults and 1 juvenile. To get them to my dorm room, they had to survive a car drive to my house and then a train and bus trip to my dorm. They got there safely, and they're already happily swimming around.
This is what my aquarium looks like now, with the 6 small Endlers in it.
These fish are very lively, they are swimming around and playing with each other all the time. It's very entertaining to watch, but hard to take pictures of.
Here's a short video of my aquarium: