More specifically, you should look for a Marabou fan, which is a type of folding fan trimmed in feathers. Wrap tape around the bottom of the fan to hold it open as you work.  Look for a Marabou fan with bright blue or green feathers if you want a brighter, more colorful peacock costume. This would be especially fitting if you intend to make the costume for a child, but this can be used for an adult costume, as well. If you plan on making this as an adult costume, you could look for a Marabou fan with black feathers for something a little sultrier. For added authenticity, you can even look for a Marabou fan that is trimmed with peacock feathers. Use a hot glue gun to glue the tips of 12 peacock eye feathers to the tip of the fan.  A child-size tail will need a total of about 50 "eye" feathers and 50 "sword" feathers. An adult tail may need several dozen more. The feathers should be between 30 and 35 inches (76 and 89 cm) long, but you may need to trim off up to 12 inches (30 cm) for a child's costume. Alternate which side of the feathers faces up so that both sides look nice when finished. Use a hot glue gun to glue the tips of 11 peacock sword feathers to the tip of the fan. Place the swords in between the eye feathers.  The sword feathers should be slightly shorter than the peacock eye feathers, but only by 1 or 2 inches (2.5 or 5 cm). Turn the sword feathers so that they are angled in toward the center. "Sword" feathers refer to peacock feathers that have the traditional coloring of a peacock tail but not the trademark "eye" pattern at the upper end. Continue adding peacock eye and sword feathers until there are very few, if any, gaps remaining in the tail.  Apply hot glue to the stems of the remaining layers. The stems should not only be fixed to the tip of the fan, but also to the feathers of the fan and the stems of lower layers. Glue the peacock feathers on in layers. Many of the stems will overlap. Use hot glue to attach a piece of thick cardboard over both sides of the plastic portion of the fan....

TL;DR in Indonesian:
Dapatkan kipas tangan lipat. Rekatkan bulu mata merak ke kipas. Tambahkan bulu-bulu pedang merak. Isi celah yang kosong. Tahan ekor-ekornya bersama dengan kardus. Tutupi kardus dengan kain.