In the DMG on pages 128–129 are rules on magic item crafting by player characters. However, there isn't really a way to create cursed magic items given. Are there any official sources for player characters creating cursed magic items?
There are no details on this process in any official resources. The closest thing is that the Bestow Curse spell can have effects beyond those listed in its description, subject to DM approval, and that spells related to a created item (in this case, Bestow Curse) must be cast by the creator each day of the creation process. This leaves a lot of details up to individual DMs.
Yes, there are rules listed for crafting magic items in the DMG on pages 128-129 as you rightly pointed out and RAW it doesn't specify curses. But with this in mind it sets out a structure and rules around creating magically enchanted items. So using this rule set as a guide you can be as inventive as your DM allows with what you use to curse the item.