Aquarium Adventure is a nice, clean, well stocked store! It's located on the East side of Glen Cove Road just north of the LIRR. I've rarely seen sick or dead fish in any of their FW
tanks, and their selection is pretty good. They're a bit on the expensive side, but they offer an annual discount membership for $20. With it, you get 25% off livestock and plants, and 10% off equipment, food, and supplies. They also have special discounts and close-outs available only to members. You just gotta do the math to determine whether the membership will be worth it for you.
Another nice store a bit closer to you is Fishtown USA in Flushing. It's located on Northern Blvd near Francis Lewis Blvd. I wouldn't be surprised if they carry keyhole cichlids too.
You may also want to put the word out at GCAS when it starts up again next month. I'm sure that one of our members are breeding them. I also hope that you get set up with some nice koi angelfish this year. Be sure to make the September meeting because people will be bringing a whole summer's worth of home-bred fish to auction off!