If you can’t find Korean cucumbers, English cucumbers will make a good substitute. Both types of cucumbers have thin skin that isn’t bitter. They also have fewer seeds and a crunchy, slightly sweet flavor.
Remove the seeds from the cucumbers to prevent the salad from getting overly watery. The seeds will also add a slightly bitter flavor.
You can replace the chives with 3 green onions or a small bunch of Chinese garlic chives.
Gochugaru is Korean chili powder. It is less spicy than other chili powders and has a slightly sweet, smokey flavor. It is hard to replace the flavor of gochugaru with other chili powders.
For a slightly more complex flavor, you can use Gochujang paste which contains gochugaru powder but also has some bold, fermented flavors.
If the dressing is too spicy for your palate, replace half of the gochugaru powder with paprika powder.