These are my suggestions, not sure what others think. It will also depend on the context:
1) I could care less
2) I don't give a ______ (care, darn, cr(xx), sh(xx), da(xx), fu(xx)
3) And you're telling me
because... (in response to what someone else said)
4) I could give a care
5) So/So what?! (Response)
6) Why should I care?!
7) like I care!
I hope this is what you're looking for!
-Heather