You can try searching on fanfiction websites like Archive of Our Own (AO3). They usually have a wide range of fan - created works, including Batman x Copperhead fanfics. Just use the search bar and type in the relevant keywords.
It could be about an unexpected alliance. Maybe Batman and Copperhead are forced to team up against a common enemy in Gotham. This could lead to some interesting character interactions as they have very different moral compasses.
You can start by looking on fanfiction websites like Archive of Our Own (AO3). It has a large collection of fan - created works, and you can search specifically for Copperhead Batman fanfiction there.
Another option is to check out Reddit. There are subreddits dedicated to Batman fanfiction. You can post a request asking for Copperhead fanfictions. Fellow fans might be able to recommend some great ones they've come across.
You can try fanfiction.net. It has a large collection of fan - fictions from various fandoms, including 'batman x superwoman' ones.
One common theme is the battle of wits. Batman is known for his intelligence, and Copperhead is no slouch either. Their encounters often involve outsmarting each other.
There could be many interesting fanfictions about Copperhead in Batman: Arkham Origins. One could be about her backstory before she became a villain in the game. Maybe she had a difficult past that led her to a life of crime.
You can start by looking on Archive of Our Own (AO3). It has a large collection of fanfictions, and there are quite a few 'Batman x Riddler' ones. Just use the search function and type in the relevant tags.
In some fanfiction, Copperhead could be a reformed criminal who seeks Batman's help to take down a more dangerous criminal organization that she once was a part of. This would involve a lot of character development for Copperhead and an interesting dynamic with Batman as he decides whether to trust her or not.
A theme that is also seen is the exploration of Copperhead's abilities. Fanfiction writers might play around with how her snake - like abilities work in different situations against Batman. For example, how she uses her flexibility and venomous attacks in a fight, and how Batman counters these unique abilities with his own skills and gadgets.
Some specific forums or communities dedicated to the work that Copperhead is from might also have fanfic recommendations or even host fanfics themselves. For example, if Copperhead is from a comic book, check out the official or unofficial comic book forums.