amazing, thanks!!
Here’s the panel
I think what might be tripping you up is ない is short for ありません．And in addition to “there isn’t one” it can be used to say “I don’t have one”. Nobita comes running asking Doraemon for a balloon (ふうせん出して), and so from that context we can assume Doraemon means the “I don’t have one” interpretation of ない
なんか can depend on context. At the beginning of a sentence, it might be an exclamation associated with emotion.
Here after a noun and especially with a negative adjective, it has a bit of a “such like” meaning
A rough translation: I don’t have anything like a balloon