¿Dónde se puede comprar eso? En ninguna parte.

Question

¿Dónde se puede comprar eso? En ninguna parte.

Se here, impersonal or passiva?

Answer 1

This is the impersonal construction - Where does one buy that?

I suppose this could, technically, be the reflexive construction as well - Where does he buy himself that? (Buy that for himself). But, if that's technically possible, it would have to be used in an overall context where it made sense. For instance, maybe someone wanted something for Christmas and no one got it for him, so someone else asked where he could get it for himself. (Nowhere, it turns out).

Taken by itself, the sentence would most probably be the impersonal construction.