The best way (the one that worked for me) is to buy at least half dozen juvies and grow them out. I bought 1" juvies, and a pair had formed and started spawning at between 2 "(female) and 3" (male) took only about 6 months, and they remained bonded a long time.
I was able to get young bean in the Chicago area for about $3 each.
I had tried a year earlier with what was considered an adult (6") bonded pair, which ended in disaster.
From the spawns, of the group grow out pair, I ended up with many fry, that I found were very difficult to give away, unless I shipped.
below young female in spawning dress at only 2-3".
her first spawns fry,
Mine came from a very well known midwestern cichlid breeder called Place Pete
Gunpowder Aquatics has "Green Guapole" Beanis for sale, I myself never owned any but they are definitely on my list of fish to get in the future, I'm just waiting to get another tank set up for they will be in a species only tank,, good luck