If you are going to translate it like that, then "...is it not?" sounds better to me than "...is not it?"
But, I like "..., isn't it?" or "..., right?" much better.
Yeah, you can say "isn't it," which is technically "is not it," but if you break it up, you'd say "is it not?"
Oder used in this context has no direct translation to english, but this thing wants specific ways of wording the meaning. Why can't I just write "or?".
In this case, it doesn't mean "or". It means "isn't it" or "right".
I ended with "or what?" which I think would be a valid English translation.
that'd be 'oder was?'