Is there an item to change your username?

There used to be, but now you do it from this page.

It costs 1000 csc to change your name though.

I saw I just don't want to spend 1000 csc to do it

It is also possible with the from the but you have been a member for a week according to your profile and you won't get one till 2 years of membership.

Wait a year to get a loyalty totem for being registered on the site. You can pick the totem to change your name and it's free.

You might want to start using Morty Cards and saving the CSC. You'll probably get the 1000 CSC for a username change before you'll get the loyalty box in two years.